I'm currently running 320bhp on MY99 turbo with a VF28 turbo, however I've seen P1's running the same turbo at 350bhp.

I was thinking of changing my up pipe and headers to stainless.

Would this make any difference? Would I need another remap to get the most out of these mods or is it my injectors that are maxed out at 320?

 

injectors should be ok to 350 as they are 440's. P1's have different heads and valve train to your MY99 (presumed UK car) so will produce more power anyway, you will need the same heads and cams etc to get any where near with the same turbo and injectors! Ported headers will make a bit more power but aftermarket headers could send you in the wrong direction if you don't accompany them correctly!!!!

 

Theoreticly 440's will get to 350,not the case in most parts due to other factors,mine are pretty much maxed out below 350...agree ported headers and uppipe will improve the overall drive if not peak numbers,the drive is what counts though,well worth the money/effort to do