Hi all, I have a 2002 A6 4.2L with 75000 miles on it. I replaced the air filter today with a K&N, and i started it up with the hood open just to listen for any problems. I noticed a rattling noise from the engine seeming to come from the intake manifold, and it reminded me of the noisy timing chains the GM Quad 4 engines have. She will be getting a timing belt change and a new water pump before 80K miles (not done yet). Oil level is right on target, and I am worried that the lifters are getting worn. What do you think this may be?