Well from research I've read about people spending tons of money going all motor on the 420a and only getting 170-180whp and thats with all the basic bolt ons (CAI, exh mani, cat-back,etc...)higher compression piston 10.5:1 or higher, cams, etc... Found out the only way to make power with the 420a engine is to either use Nitrous or turbo it. With just a turbo kit you could make 180-200whp just on 5-6psi.