Probably one of the few honest performance mods you could do would be a HV3 insert from ZZP. It costs $200 and a fairly simple install, and your PCM doesn’t need to be modified.

Another fairly good one might be a tranny shift kit from TEP. They cost like $65, and people in general seem to like them.

On a side note, if anyone can get you a tuned PCM without giving your car a lobotomy let me know! Please. I tried some time ago with Overkill, long story short I’m still stock.