Hey,
I am brand new to the forum and have used it to do some research on an A4 2.8 Quattro that I am looking at buying. It is a '98 with 106,00 miles and in really great condition. It has been well maintained with a new timing belt at 80K and the control arms have been replaced. I ran a Carfax and it came back clean. It has some aftermarket wheels as well as a Magnaflow exhaust which has a nice sound to it. I did a thorough check of the car and all appears well except for the CEL. The owner said that the CEL is on because with the magnaflow exhaust it doesn't have one of the downstream o2 sensors as the exhaust had no place. I decided to take the car to Autozone and have them run a scan to see what the CEL light was all about and it came back with three codes: P1136- Long Term Fuel Trim Add. Fuel B1 System to lean, P0411- Secondary Air Injection System Fault, and P0455 - EVAP Large Leak Detected. It sounds like most of them deal with a vacuum leak of some sorts, but would any of these be a sign of a missing O2 sensor? And if there was a missing O2 sensor would this effect anything other then the emissions (which I don't care about since where I emissions tests aren't required)? While test driving the car everything appeared and felt to be operating normal. I just want to get some input from the pros of audiforums.com before I make the final decision on the purchase. Thanks in advance!!!