I'm guessing you meant, rx8club.com, and yeah. I am a moderator of the fc3s_org (2nd gen RX-7) Yahoo group, and probably have made close to a 1000 posts there, I'm not nearly as active on the RX-8 forum.
Mazda learned from all the modding and tuning that had been done to the 13B engines over the years. They incorporated just about all they could into the Renesis. So yeah, there aren't many gains to be had that Mazda didn't explore themselves.
Handling can be improved a bit though, stiffening the chassis (Mazda did this in a few special cars), better suspension components, and just going to newer tire technology (I have Bridgestone Potenza RE970AS Pole Positions), and even though they are all season (a dedicated summer tire can be even better, but don't dare drive them when it gets down into the 40s) they stick incredibly well, and move water off the road like nothing I've ever felt.
