When it was stolen, the ignition had been cut and hot wired and the theives had put about 25 hard hours on it. After I recovered it, I noticed a "pinging" sound in the engine and a loss of power. It almost seems like the rev limiter (?) is maxing out at 1/2 throttle. The inital accelleration is still as powerful as before. Any ideas on what I might be able to do?