Vitara pistons won't hold 350whp for long at all.. it's cast aluminum. Not forged.

Highest WHP out of any SOHC XXXX D-series was a guy from UTAH.. 611WHP, top mount, t4, 82mm D16Z6 with a 1.7L crank, and 34psi. Guy spend a SHIT-TON of money on it.