Diesel trucks are known for being workhorses. These oil-burning powerplants make power by compressing the air in the cylinder to the point that it is super-heated. Then, the injectors shoot a spray of diesel fuel into the cylinder filled with that hot air. The hot air then ignites the fuel and pushes the piston down. So unlike a gas engine that uses the spark plug to ignite the fuel, a diesel uses a very high compression ratio to do it. Knowing that diesel engines have lots of compression on tap, the aftermarket industry has found ways to shoot the torque numbers skyward.
Gale Banks Engineering is a company known for adding grunt, but with the price of diesel fuel going up, the company started tweaking the parts it sells to also add better fuel economy. Such is the case with the Six-Gun Bundle, which includes a Ram-Air Intake, Monster Exhaust, and a PDA Tuner all in one part number. Forget mismatched components; everything in the Six-Gun Bundle is engineered to work together to maximize your engine's power and efficiency.
Our guinea pig for the Banks...
Our guinea pig for the Banks Six-Gun Bundle is an '06 GMC Sierra 2500HD equipped with a 6.6L LBZ Duramax Turbodiesel. The truck has been doing a great job towing a pretty heavy trailer, but the pain at the pump was getting out of hand. After the goodies were in place the truck had all kinds of power on tap, and we saw a gain of 2.2 mpg on the highway.
The bundle replaces factory airflow restrictions with free-flowing components that increase intake airflow and air density and expel the exhaust with virtually no backpressure.
The company balances the improved airflow with fuel tuning that delivers up to 54 percent more horsepower and 68 percent more torque than stock. This is tire-smoking, scenery-blurring power that keeps its cool and still delivers better mileage. We saw an average of 12.5 mpg in the city go up to 13.5 mpg, and the highway average went from 14 mpg to 16.2 mpg on an '06 GMC Sierra 2500HD with the 6.6L Turbo Duramax. Those numbers are impressive by themselves, but take into account you will be 12 truck lengths ahead of a stock truck at the end of a quarter-mile drag race and they get even more impressive.
We took our bone-stock GMC to the Banks facility in Azusa, California, to have the professional technicians install everything while we snapped the pictures. Even though the install took the better part of a whole day, it is still geared toward the do-it-yourself guy. All you will need is a decent set of tools and the common sense to read all of the instructions before starting. If your toolbox isn't up to snuff, check out the Banks website. It has a link to approved installers across the country and hopefully one in your neck of the woods. Our local shop happened to be the manufacturer-aren't we lucky?
What's In The Box?
The Banks Six-Gun Bundle is three proven sets of parts all combined into one big ol' box. The Banks engineers have spent years tweaking these parts for optimal performance, all without becoming unsafe and melting down your motor. You get a Ram-Air Intake to fill the motor full of nice fresh air, a 4-inch Monster Exhaust to expel the spent gasses, and a nifty PDA Tuner that tells the computer what to do with all of these new parameters.
 1a.The technician decided...  1a.The technician decided to start the install with the thermocouple , which monitors the exhaust gas temperatures (EGTs) and lets the new system know if things are getting hairy. If the EGTs start getting too high, the Banks system will start pulling things back just a bit until everything is optimal. The thermocouple will be mounted into the stock exhaust manifold, but not before a new hole is drilled . | 
1b. |  2.Once the 7/16-inch hole...  2.Once the 7/16-inch hole was drilled and the metal shavings removed with a magnet, a 1/4-inch NPT tap was used to make the proper threads. The tap was coated in grease to catch most of the shavings, but the magnet was used again just in case. One thing we don't want is metal shavings running down the pipe and entering the turbo. When the tech was sure the shavings were evacuated, he installed the thermocouple. |
 3.The wiring for the thermocouple...  3.The wiring for the thermocouple is a little short, so Banks includes a set of extensions that bolt together and are covered in supplied shrink tube. |  4.The Banks Six-Gun brain...  4.The Banks Six-Gun brain box features factory-correct plugs for an easy hookup. All that was necessary was to unhook the factory plugs and snap in the Banks stuff. |  5.This is what the setup should...  5.This is what the setup should look like if the instructions were followed. If you try to move the location of the box, it might hit the hood when it's shut or the wiring might become too short. Just put it where it's designed to work. |
 6.There is a small wire harness...  6.There is a small wire harness that needs to enter the cab for the PDA. Sneaking it by the large grommet in the firewall was the best place to let it enter. |  7.The other end of that wire...  7.The other end of that wire was routed behind the cluster and popped out on the bottom right of the dash trim. The PDA mount is designed to mount here so it's easy to see and access. The mount is held on by a few small self-tapping screws. |  8.The provided PDA is turned...  8.The provided PDA is turned on and the tech made sure everything was ready to go. |
 |  9.Moving back under the hood,...  9.Moving back under the hood, it was time for the Ram-Air Intake portion of the install. After the factory airbox was removed, the new filter housing was lowered into the area. It is held on with the stock bolts removed from the airbox tray, so hopefully you didn't throw them in the trash. |  10.The filter housing cover...  10.The filter housing cover with the new washable filter was dropped into the filter housing and bolted together with the provided hardware. |
 11.The stock MAF sensor was...  11.The stock MAF sensor was transferred to the new intake tube. Included in the Banks kit is the proper T20H Torx tool for this swap. Care was taken not to damage the MAF during this process by being very gentle with it. |  12.The intake tube was secured...  12.The intake tube was secured to the turbo intake tube, and then the two new tubes were joined by the Banks Bellows. |  13.The last step in the Ram-Air...  13.The last step in the Ram-Air Intake was to plug in the MAF. |
 14.The new intake system will...  14.The new intake system will let the motor suck in all kinds of air, and the provided air filter restriction gauge will help you keep tabs on the air filter. |  15a.Getting underneath the...  15a.Getting underneath the truck for the exhaust was made easy thanks to the lift. If you don't have one, make sure to use a sturdy set of jackstands to hold up the truck. The tech used a reciprocating saw to cut the factory exhaust in a few sections to make removal much easier . If you don't cut the tubes, you will need to tear out the rearend. | 
15b. |
 16.The new Banks tubes are...  16.The new Banks tubes are 4 inches in diameter and are constructed out of mandrel-bent stainless steel. According to Banks, the exhaust system cuts backpressure up to 98 percent and flows up to 176 percent better than the stock setup. |  17.The new system slips together...  17.The new system slips together and is held by large clamps. To make sure there is enough pipe slipped inside, the tech uses the three-finger rule. He laid three fingers on the pipe and marked it with a pen. Now he knows how far to slide the pipe before tightening the clamp. |  18.To finish off the system,...  18.To finish off the system, a huge 5-inch polished-stainless-steel tip is installed. The tip has a rolled edge and double-wall construction. The double wall keeps heat from tarnishing the exterior mirror finish. |
The Final Word
With everything installed, we pulled the truck out on the road and pulled the trigger. The truck took off with a nice deep growl, and the smell of burnt rubber filled the cab. It was hard to believe this was the same truck, especially when we calculated our mileage. We guess we know why Gale Banks decided to call this system the Six-Gun. We wonder if there is a Rocket Booster system in the works.
The proof is in the pedal and the pump:
Stock
City: 12.5
Hwy: 13.5
Six-Gun Bundle
City: 14
Hwy: 16.2