Hey Nick

I got the STi Hood scoop and purchased a zerosport splitter (more fins on a better angle to direct more air flow to the intercooler)

I think the splitter is there to ensure that all air is put in to the intercooler rather than going aroung it.

Im no car buff but i would say you need iT to maximise the intercoolers potential.

As for the y pipe - i have been told that the sti y pipe is the all you really need - if not samco silicon hoses from hyperflow have these - speak to steve

Cheers

Chris