The Gen III LS1 engine factory-installed in '98-'02 Firebirds, '04 GTOs and the Gen IV LS2 between the fenders of the '05-'06 GTOs are excellent powerplants. Current LS2 engines are rated at 400 hp ...
Equipped with a 400-horse, all-aluminum, 364ci LS2 powerplant, an '05 or '06 GTO is a sophisticated modern-day musclecar. Dubbed a "Gen IV small-block" by GM, the LS2 took the LS1's bore of 3.90 ...