I have yet to be "WOW'd" by any mods performance-wise. (My butt-dyno must be getting fat, old, and cynical...) I must say that the Trifecta transmission tune came the closest though. A close second is the Vararam - not for the performance - but for the change in sound at WOT. I haven't had any issues with the Trifecta tune, my car is running well; but I've read about people feeling that things got better for them after taking it off. I must admit I would like to get an wideband AFR gauge on the car because I've also read about a lean-running issue one member on here had with a Trifecta tune. But that may have been particular to his car/application.
Vararam | Vmax Ported TB | Ported IM | Vmax Black ICE-olator | Trifecta Tune