Originally Posted by cpt97m3
That would all depend on how good the person doing the inspection did the visual test. If they noticed they downpipes were not OE, they could fail you on visual. That's not a super easy part to see, so that helps. But last time I had the M3 checked, the guy spent 15 minutes looking that the exhaust part by part with mirrors and such. It was all stock, so he didn't find anything, but he told me they do look for aftermarket parts and missing cats. So just make sure your downpipes look exactly like the OE catted ones on the outside, and you should be good.
Aren't the DPs very hard to see anyway, unless you jack up the car and look beyond the plastic covers?