Quick little DIY on the M54 6 cylinders valve cover gasket. Sometimes the covers themselves have very small hairline cracks that cause intake leaks and check engine lights. I've had to replace the entire cover on 2 cars so far, and they're not cheap ($350).

If you can get away with just a gasket, consider yourself very lucky!

https://www.youtube.com/watch?v=XkNaNGtnyYU

May as well do the spark plugs while you're in there:

https://www.youtube.com/watch?v=sjAojOoi_ZQ