I think any mod under the hood other than cold air intake and exhaust upgrade would void most new car warranty, not too sure about that, but I'm sure turbo and performance chips will. Some brands don't even allow cold air intake kit, unless you buy their upgrades.
I know the last model RX-7 was twin turbo, putting out 280+ ponies. it was supposed to be the same basic 1.3 L engine form the 80's. But I don't know what they did with the RX-8. I wasn't looking for a fast car, just a nice convertible. BTW, I hate speed bump now, high gas prices not helping either.
Lightning, my other car is a camry, smooth ride and very quiet. only down side is I keep sticking my key in the wrong car at work.
At least mine don't attract police like some red car does.