standard list, a boost gaugeand boost controller(electronic is best but pricey, or a mechanical relief valve. dont use a bleed valve, takes longer to build boost), stainless de-cat downpipe, and a bov. that should get you around the ~280 bhp mark. Other worthwhile bang-for-buck mods include full cat-back exhaust (hks or mongoose are favorites), and a straight air intake with cold air box and cone filter. With all that you could potentially be pushing around 320 bhp. You could aslo opt for a FMIC but the st205 chargecooler does a great job and FMIC is a tricky job.
But before doing any mods, make sure engine and box are in good condition and been maintained well, regular fluid and belt changes when necessary.