I bought this car about 7 thousand miles ago and have spent more than 2 grand fixing all the randoms on this car to try getting it working right for longer than a week at a time. I just bought it recently and even drove it from NC to MI and back twice. BUT I have gotten the crank shaft position sensor fixed twice, new plugs, new coil packs, new battery, always good on getting oil changed. The auto shop I've gone to has been playing me. My car will not go over 20 mph without misfiring. This time they are trying to say i need a new knock sensor, which i bought, and when they tried to change it they told me they couldnt and that i needed the gasket manifold changed too?? I know nothing much about cars and im getting multiple "it could be's" by this auto shop. I have it at home. It starts but will not accelerate without misfire, NO CHECK ENGINE LIGHT! VSA light will turn on with it while misfire light blinks as well. It just started doing this again and not just a week ago did i replace the plugs and coils.. Im thinking it was possibly a mod car because theres some random parts in the engine that im not sure of. HELP WHAT COULD IT BE FOR REAL?