My buddy had a 91 SI that he threw a cheap ebay turbo kit on, custom fabbed a side-pipe exhaust, did up the suspension and went racing. Tons of fun, never tuned. It was about as quick as my bone stock 2001 Miata around the track.
He ended up selling it to me, removed the turbo kit, and I daily drove it until the head gasket popped and this happened:
I then sold it to our other friend who returned everything to stock except the suspension, put in a somewhat fresh motor and has daily driven it for the last year. Awesome little cars!
In other news, any idea when the charge pipes will be ready, Russ?