8. The new Firepower ignition system will facilitate a plug gap of 0.065 inch. The larger plug gap leads to a more complete combustion of your fuel mixture, which, in turn, provides more horsepower, better gas mileage, and cleaner spark plugs. After gapping all of the plugs, I installed them, plugged in the LiveWires, and fired the truck. Now things were getting better. The stumble was gone, and the 4.3 was revving like a champ.