B18 or B20

You wont get much of a gain on this manifold on stock motor. The manifold doesnt start to produce power until 7000rpm. Well, you and I know that the rev limiter will prevent you from seeing those gains. This might be different in somebody else's case but my friend did not gain a thing on his stock motor.

Recommendations

Crower Cams, Springs, Retainers, Gears, ECU w/o rev limit

After all these mods were done in conjunction of the SK2IM, we saw 13 peak WHP at 7500rpm.

I dont have any experiences with GSR motors so I cannot help you there, good luck. --Migs