You may want to clean out your air filter before 55K miles.
 

I just did the 55K service myself and could not believe all the junk in the air intake, air filter and filter box. I should have cleaned this out at 25K and changed the air filter. There is also a small screen in the air intake pipe that was clogged with leaves and other debris. The cabin filter was filthy too. Clearly Audi pushed this service back past the free maintenance point to make money but IMO it should be done sooner. Both filters are very accessable and easy to do yourself. The spark plugs are more of a challenge, mostly the part about getting the wire harness clips to let go of the coils.

Thanks for the info. How does one access the cabin filter?

The cabin filter is under the hood on the passenger side at the base of the windshield. Takes a minute to open it and change out the filter.

When I bought my car at 22k miles I cleaned out the airbox and the amount of dirst, dust, rocks, bugs, sticks and random stuff blew my mind. The design of this intake is flawed and allows for WAY too much debris to accumulate.

Not all cars have them. My 2007 doesn't have a cabin filter.

I was just at the dealer and the service guy said they change out all filters at 45k (which I'm due for in a month or so).

A cabin filter is standard equipment. If you're missing one, then it was taken out and never replaced.

Not true. Starting in 2007 the eliminated them from the A4 to cut costs just like the color display on the dash.

I cleaned it once a year atleast. Changed my AFE filter yearly

I just bought the drop in AFE dry flow... that mesh screen on the 'snorkel' part of the air duct was stuffed with leaves/debris. I'm at 30k miles.

AFE filter seemed to make ZERO difference according to my butt dyno :-)