2001 Audi A6 2.7 @79K. It now has the infamous whistle (some say 747 sound) of a secondary air injection pump not working correctly. There’s not much doubt about what is going on. But what are some things to have checked before just buying and installing the expensive pump? Fuse? Solenoid? A short near hot spots? Bad connects?
Also, if you can stand the sound is it OK to let it be?
If an emissions test is not part of your life, you can simply remove that mess and all it’s plumbing…The resulting CEL is easier to live with than the 747 sound…