Theres no way from what ive read on VQ35s for them to make 350BHP from stock with just the usual supporting mods. Big loud cams, fueling, injection, porting, polishing, skimming, timing and a whole shop of other parts then maybe, just maybe. But you're talking about upping compression, a serious N/A build. And absolutely thousands of pounds for when as coldel says, put on either a turbo or supercharger and youll make more for less.
The uprev isnt just about unlocking modifications, its about improving the entire feel of the engine and how it drives. This really frustrates when people make outlandish claims and people believe them!