Hello everyone. I just had my local mustang speed shot install a set of JBA shorty headers, shorty h-pipe (with MIL eliminators from American Muscle) and flowmaster catback. The shop told me that one side of the rear o2 harness was very short (maybe since it’s automatic) and had to be extended for the h-pipe install. Everything sounded great and went well until the drive home where about 15 minutes into the drive I got the dreaded ‘check engine’ light. I ran codes at Advanced Auto Parts and codes P0054 and P0442 popped up. I know that P0054 is related to one of the rear o2 sensors…not sure if it’s from the guy rewiring the o2 extension or the MIL’s just not working right. I’m not sure where the P0442 came from because that indicates a small leak in the EVAP system. Not sure where to go from here as the car seems to run fine (idles slightly lower that before though). Any help or thoughts on this would be greatly appreciated as I don’t have much knowledge on 4.6 mustangs. Thanks