Ok, my friend got in his 98.5 A4 1.8T Tip this afternoon to move it out of his driveway, and when he started it, it had a harsh idle and made a very low volume yet high pitched whistling. It also gave off a cloud of very bad smelling exhaust smoke. He opened the door, and called me over to check something out. He showed me that the check engine light was on. His owner's manual stated an error in the emmision control system could be the fault. It is going in tomorrow, but I am just curious if this has happened to anyone? The car has near 8000 miles only, and is not driven too hard. What could be the problem?

Thanks in advance guys. We both appreciate it.
DrBimmer

Just guessing, but from the high-pitched whistling, would bet that a hose (possibly vacuum)disconnected/broke off at/by the Turbo, totally screwing up the airflow or measurement.

Ah, the joys of Turbos!