Concerning the 1993 Mazda RX-7 Twin Turbo, I had one for about 3 years. The top speed, according to Motor Trend or Car and Driver, was 160 mph. I probably broke 100 mph only once or twice. Anyway, it takes a lot of extra horsepower to go from 160 to 172. Those cars are fast and they handle great (on dry pavement anyway) but I read too many advertisements for cars that had the engines replaced. I was told that replacing the turbos alone was over $3,000. So I sold it and now I have kids instead.
Dave
