as said, giving a good service is always a good thing. make sure you replace all the vacuum hoses too for some silicone stuff (the ones for the map sensor and FPR tend to perish after time.
oh, and to get the best out of the 16v you have to welly it.. i found that you really need to keep the revs above 4k to get the power band.
a decent panel filter and modified airbox will also give you good results, then perhaps a decent exhaust. then dig deep and go for proper mods such as boost...