A little background before I ask my question. I've had an intake for a while and added a Y pipe back system two weeks ago. I rarely ever get beyond 4,500-5K rpm in my car.
Yesterday while showing the exhaust to a friend I ran it up to redline in third gear. Beyond 5,500rpm I felt a mild power hesitation or a sort of sudden "drop off" in torque. It still was able to get to 6500rpm without issue but the car was running noticably rich blowing greyish/black smoke At the point where a performance drop occured. Other than that there is no smoke at idle, normal driving condition, or free revving. The car still performs and drives the same without any lack of engine performance. I haven't attempted to duplicate the effect again though I was wondering if this is normal considering the car doesn't see that high of RPM frequently?

Thanks

 

sounds like you just blew out some stuck carbon deposits. You should def. wind out your engine every so often.