i wona get the perrin intercooler silicon hose kit 4 my my03 sti, but i can only find it 4 the wrx., will it fit?

you don't need it.

Theres not much point as the STi already has a silicone/aluminum y pipe, you would only get use from the BOV return pipe & IC to manifold hoses which you should be able to buy separate.

yeah but i got a hole in one of the pipes so i though i might as well replace all of them at once...