I have tried three differnet n75 valve(c,j,and h) to cure my surging problem and they all work great. No surging, pulls all the way till redline. After Im confident that I have solve the surging problem a few weeks later my car runs like crap again, surging, poor throttle response and inconsistant throttle response behavior. Is this normal? Drives me freaking crazy. Whats going on the first few weeks that makes my car run well? Why dosn't it stay that way?