I have 2001 Mustang GT that i bought a few months ago from craigslist. When I first bought it, the car ran great, I could hit redline no problem, but then the first time I took it to the track for drifting I started having problems. After a few runs, when i would clutch kick the car had absolutely no power and i couldn't break the tires loose. Then i took it off the track to test drive it and the car would not go past about 3k RPM. The drive home, i could hardly give it any gas or it would sputter almost like a misfire and especially up hills. But then after a few days it went back to normal. Then i took it back to the track a few months later and the same thing happened. This time the "misfire" wont go away. It really only happens when i give it hard acceleration like a hard shift or if im off the gas and then floor it immediately. I have changed the fuel pump, fuel pump module, Fuel rail pressure sensor, spark plugs, coil packs, throttle position sensor, crankshaft position sensor, and idle air control valve. Please if anyone has any advice, let me know! Thank you!