Did you use a name brand gauge to test? I used a junk Chinese brand and my back pressure tested ok as well. The only time I saw abnormal back pressure readings was when I'd be at 2k rpm and then rev is fast to 4k or so. I still believe your cats are the issue. The code you are getting is the classic code. The BMW specific code is 28a2. Can you pull the BMW specific code using something like pa soft?We I checked the pressure on the cats and the pressure was good. Was told they weren't clogged. Now I am wondering if the downstream O2 sensors are bad and that's causing the problems. I didn't realize the down stream O2 sensors were connected so far away from the cats. Order two new sensors today so I will try that out and see what happens. May need to replace the upstream O2 sensors as well. Thoughts???
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