ELEVENS

When I say valve I mean the vacuum-controlled solenoid valve that controls the flaps. There is one mounted on the rear end of each muffler.

In the attached pic you can clearly see the vacuum hose attached to it.

SprintblueRS4

OK, thanks for the info. So to summarize, either its a faulty valve or need some penetrating fluid to open. Last question - why am I not getting a check engine or fault for this?

s4master1

the computer check for pressure difference in the vacuum system, as long as it holds vacuum it sees all working fine, if you disconnect the hose it will cause a fault.
on aftermarket exhaust you just plug the hoses and avoid having check engine light on.

Winterrunner

You wont have a CEL, it is the vacuum system, and according to the computer, the vacuum is holding....

Reggie

It might still be worth a check with a VAG-COM to see if there are any errors.