I am looking at purchasing a 2001 A6 with the 2.8l. The owner of the car told me that it is throwing a "cat out of range" code, and that he replaced the O2 sensors trying to fix it. I have read that this can be caused by the coolant sensor malfunctioning, causing the car to run rich. However if the cats really are bad will the car pass emissions with test pipes? I have heard of using spark plug non-foulers, and tweaking the computer to make it say every thing is okay. Will either one of these work here in IL? They use the OBD port for emissions, the sniffer is only used on older cars.