In January my '95 525 failed the state emissions test for HC and NOx at a local Kwik Lube place. I took it to a local BMW indy (Lone Star Bavarian) who looked over the results from the printout and thought they were suspicious. He took it to a place that knows BMWs and had them redo the test. It passed with flying colors.
The indy told me that it's pretty rare for a well maintained Bimmer to fail emmisions. From now on I'll take my car to a place that knows the type instead of the local place that just happens to have the equipment.