New GM LB7 Crate Motor w/ 63mm Cheetah. BAD FUEMILEAGE
I recently installed new GM Crate LB7 in my 2004 2500HD 4x4. ZF6 trans w/ std injectors, stock pump, 63mm Cheetah Turbo, MBRP down pipe and factory exhaust. No tune as of yet
I get 11-12 mph in town and 13-14 mph oh highway. Truck used to get 20 mph.
Please help, need to know how to improve fuel economy.