An instant 20-30 hp would be the Intercooler buckshot77 is developing for his SC 3L and will probably talk me into when I recover a bit from this last mod

He is willing to sell the design once it works well on his car. A True Dual exhaust with gutted pre cats (mystery mod) will help a lot as well, probably 5-10 hp right there. A free mod would be Throttle Body optimization following the How to on the site or send it to Buckshot77 again and he will do it for a small fee.
Eitherway though man you have A LOT of HP there! I am hoping for just over 300 FWHP on my SC 3L! Of course I'll clobber you in TQ, but I bet our HP won't be far off! That's amazing from a 2.5!