It's a toss up between the AS+M -
Arizona Speed and Marine has taken the time to ensure that these are the best headers for the newest GM truck. Extreme effort was put forth towards proper fitment, durability, and performance. They have produced gains of 22 horsepower and 25 ft./lbs. of torque on a stock 5.3L V-8. These exhaust headers are designed to work with all three V-8 engines; 4.8L, 5.3L and 6.0L. They will work on both two and four wheel drive. Features: 4.8L, 5.3L and 6.0L application; 1 3/4" Primary Tubes; HPC Ceramic Coated; Emissions Compatible; Laser cut flanges for accurate gasket seal; Includes headers, gaskets, bolts, and installation instructions. ** Does require some installation welding as documented in the installation instructions. $749.99
and The Other Guys -
You?ll enjoy increased performance and fuel economy secure in the knowledge that The Other Guys long tube headers are manufactured to the industry?s highest standards. There are no compromises in material and workmanship.
1989-2004:4.6L-8.1L
GMC, Chevrolet
Light trucks & SUV?s
14-gauge mild steel
Electroless-nickel-plated
Titanium-thermal-barrier-ceramic
Corrosion and heat resistant
1/2? thick precision-cut flanges
50-state legal
Gain of up to 43 horsepower (modified motor)
California Air Resources Board (CARB) Exemption No. D-509
Exhaust flanges are made from beefy 1/2" thick steel plate (50?100% thicker than most others) and ground flat.
Thick 14-gauge tubing is used instead of ordinary 16 or 18-gauge. Tubes are precision TIG welded to the flange.
A.I.R. refers to factory installed air pump emissions systems.
A special Electroless nickel plating is used inside and out. This is twice as durable as stainless steel. These headers are so well built, they?re backed by an un-limited lifetime warranty. - $759.99
Ceramic coating is available for $150.
Tom