how do you get the upper engine cover off, so that you can replace the air filter?
It should be held on by a few thumbscrews -- look for 3-4 plastic thumbscrews. It may also just pop off, being pressed onto posts coming up from the engine. Try prying gently at one side to see if you can get it to come loose that way.
Search Volkswagen Passat Questions
Volkswagen Passat Experts