i went back to stock from the WS ypipe a week ago, i noticed that when im warming up the car, until it gets to normaltemperature, the steering wheel will vibrate, but the RPM's are steady. it only happened after i switched back to stock, once the car is warmed up, it runs fine. could a leak be causing this, could it be that i didnt mount the ypipe and cat correctly? the car dindt do this with the WS pipe on, and it dindt do it when my car was stock in the first place, gasket might be slightly leaking from the back end of the cat conv. im not sure if that has to do with it