I had a 93 rx7 twin turbo and it was without a doubt the worst sports car I have ever owned. It was one gigantic lemon. Granted, I had an early production version, but the string of TSBs and recalls was incredible. And, the engine asthetics of the hissy, spitty and poppy turbo motor were lousy. It had a big flat spot between the first and second turbos and got worse gas mileage then my Viper. It rode like crap and rattled like crazy from the rear suspension. Overall, I worked on it more then I drove it.
However, I don't doubt that with a big enough turbo, it could have been very fast.
Jim