I'll start off. 1998 Z71, 5.7 vortec, LT1 cam, roller rockers, mpfi conversion, ported throttlebody, K&N cold air, MSD ignition, headers, high flow cats, true duals, underdrive pulleys, custom computer tune, 4.10 gears front and rear. It still knocks down 20mpg on the highway when not being...