S3 esp light + power loss

[kegstore]

OK, I've had a 2000 S3 (210BHP) for about a year now. Brilliant car, but a niggling problem has returned to haunt me.

When I bought it, there were a number of faults requiring attention, one of which was power loss when accelerating, then surging, combined with the esp warning coming on and not going out until the engine was restarted. Bristol Audi replaced the air mass meter, and all of these problems disappeared (including the esp light fault, oddly?), until last week when exactly the same symptoms started up again. Bristol Audi diagnosed a faulty air mass meter and replaced this under parts warranty, but I'm still getting the warning light occasionally (comes on and stays on until restart), combined with a slight power loss. Very odd, even the dealer is a bit stumped! Any ideas anyone?

Many thanks