So i was running an open header for about a week, waiting for my cat to come in so i could install my Fujistubo exhaust. It was obnoxiouslly loud so i wanted to see how loud it would be at redline. With an open header i could bounce off 7200 ( yes i know it wasnt smart, but it was only once or twice). I just had my exhaust installed a few days ago and wanted to hear the sound through a full range of throttle and when i went to listen at redline, the car hits a fuel cut at 6000, and check engine light comes on just like it would bounching off redline. Im not sure what changed the redline, i know i didnt bend a valve, and back pressure couldnt change it could it? Any ideas?