The pistons wont hold past 350whp from what i have seen, an from what we have learned on halfwits motor, you will not see much past 300whp without a ported cylinder head an oversized valves.

the D heads run out of steam at 300whp. I have seen guys making over 300whp on simple setups, but i dont believe it, the turbo D series world is weird.

guys with stock motors, or Vitara pistons an STOCK heads make 400whp, then the next guy with a fully built an sleeved motor, ported head, cam, only make 350whp.

but still, that kind of power is still fun cause they make so much torque.

400whp i think is seriously out of reach without a crazy head