i would say if you want 350 real kw at all 4 wheels, then you need to go for some serious turbos. we're talkin 2530's, gt-rs or perhaps a big single. In your case, i would just upp the boost a bit more. But i wouldnt run more than 1.3 bar on a stock engine (which is about what you are running at the moment). If you want to run 1.6 bar, you need to rebuild. Even then, most of the guys running about 20-22 psi are getting figures around the 300awkw mark