[A4] cam chain

[Peter Kirby]

I'm writing this on behalf of a friend with a 1999 A4 1.8tq.  He's
hearing what he describes as a "swooshing" sound loudest at about 3000
RPM, coming from what appears to be the back of the engine.  He's
wondering if it could somehow be related to the chain that connects
the two cam shafts.  Has anyone had any issues with this chain
stretching or  is there a tensioner in there that could be failing.

Sorry for the vagueness.

Thanks.

Peter