Flowtech Fantom Exhaust on a 2001 GMC Sierra - Hidden Horsepower

Unleashing the hidden horsepower...        read full caption Unleashing the hidden horsepower in late-model GM pickups is easy with the addition of the right parts.

Flowtech’s new Fantom...        read full caption Flowtech’s new Fantom after-cat exhaust system for late-model trucks uses mandrel-bent aluminized tubing, a high-flow muffler, and a stainless steel tip.

The stock exhaust system takes...        read full caption The stock exhaust system takes a lesson from the aftermarket, being made primarily of 3-inch tubing. The biggest restriction, other than the kinks in the piping, is the muffler.

One of the hardest parts of...        read full caption One of the hardest parts of the whole install is removal of the stock setup. A Sawzall makes quick work of the job.

With the stock system removed,...        read full caption With the stock system removed, the first order of business is to bolt on the new head pipe.

The muffler is added next...        read full caption The muffler is added next and simply slips over the head pipe.

With the muffler in place,...        read full caption With the muffler in place, the tailpipe is routed over the rear axle.

The tailpipe slips over the...        read full caption The tailpipe slips over the outlet on the muffler and can be hung using the stock hangers.

With the system supported...        read full caption With the system supported and aligned properly, the enclosed clamps are added.

The system tailpipe is a tad...        read full caption The system tailpipe is a tad long and can be adjusted to fit.

The finishing touch is the...        read full caption The finishing touch is the addition of the stainless steel tip.

Over the years, vehicle manufacturers have borrowed some of the power-making secrets of the aftermarket to improve their products. A good case in point is the newest line of GM trucks. Equipped with either the 4.8 or 5.3L V-8 powerplants, these trucks make great horsepower and torque right off the showroom floor.

One of GM’s borrowed power secrets on the new LS-1–based motors is the use of a high-flow exhaust system with header-style cast-iron exhaust manifolds feeding into a 3-inch exhaust system. While the new setup is good, there’s always room for improvement. Enter Flowtech Performance’s new Fantom after-cat exhaust system from the folks whose name is synonymous with performance: Holley.

Flowtech has designed an all-new line of after-cat exhaust systems for later-model trucks and SUVs that takes the design elements used by the factory to the next level. Built from mandrel-bent, 16-gauge aluminized tubing, the Fantom exhaust system improves exhaust flow approximately 20 percent for increases in horsepower and torque, while also adding a powerful sound to your truck. The system exits in the stock location and uses all the stock hangers for an ultra-easy installation. The finishing touch is a T304 aircraft stainless steel tip.

Installation is a simple R&R affair. We followed a Fantom system installation on a 2001 GMC shortbed pickup at Ace Muffler in Santa Ana, California. We also ran some before-and-after dyno numbers on the truck to verify the performance gains. The hardest part of the install was removing the stock exhaust system, which had to be cut in two pieces to get it out from under the truck.

If you’re in the market for a simple after-cat exhaust that sounds good, makes power, and can be installed in your driveway, look into Flowtech’s new line of Fantom systems.