I took my mustang down to the shop yesterday to have an O/R BX Bassani X pipe installed on my car. I currently am also running the slp loudmouth setup. The car was loud as hell and I could definitely tell there were no cats on (smell, sound). Interestingly, the check engine light was not on in my car and I have heard several people complain about this. The mechanic told me that the x pipe came with something that shut it off (which I know were not mil eliminators). Is there something I am missing or what exactly is going on. He said he fiddled with the O2 sensors also.