'07 335xi N54 E90 auto, bone stock, 93K miles. No CEL, but I pulled codes yesterday and found P0420 and P0430 pending. In no hurry to spend $1700 on downpipes; does anyone have a proper diagnostic procedure to make sure the cats are the problem here? Ways to eliminate the O2 sensors and other factors?
And I hesitate to ask, but has anyone tried Cataclean?
Thanks!
did you figure out what's the problem
????
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