I have the standard exhaust system and a set of some type of extractors (they twist around and meet in the middle.... the normal thing you see. . . . which will give be the best out of the 1500sp?
i know it wont make MUCH difference but anything helps
cheers
adz

definately the extractors. and even being a 1500sp u will still notice a huge difference.
take your time and try out both and i bet you dont go back!