The GMT800 HD trucks were a massive step forward for GM's truck division. The available engines included the LS-based 6.0L, the big block 8.1L, and the line-topping 6.6L LB7, LLY, or LBZ Duramax diesel. Whether gas or diesel, we have the parts to take your truck to the next level on the street, worksite, or drag strip.

Holley’s collection of Tuners includes handheld, in-cabin, and inline systems from leading brands like DiabloSport, Edge, Superchips, and Accel. These tools deliver instant horsepower and torque gains through precision-engineered calibrations designed for gas, diesel, and hybrid vehicles. Whether you want more towing power, throttle response, or track-day performance, these tuners put complete control of your engine management system right at your fingertips.