2001 A6 2.7biturbo. Started to start bad in the morning for the past 3 days. Starts really laggy and sputters and revs strange. Thought maybe I bought bad gas so I put in some Heat and Octane booster and Injector cleaner. Anyway, after it finally starts, it runs fine all day. Next morning, same thing. Thought maybe a fouled sparkplug, but not sure. Will get my OBD scanner out and post the code tonight. Any thoughts off the cuff?

 

Well, it turns out it was some bad gas. Caused a fault reading in the "warm-up catylist". Anyway, ran the gas out and filled back up with 91 oct. from a respectable gas station. Reset the check engine light with my OBD-II scanner. Started up just fine this morning. No check engine light. Yeah!