A few months ago the CEL came on in my A3 2.0 FSI. Turned out to be an under boost code. The car ran fine, so considering money is tight and the car is out of warranty I just shrugged it off.

Now the turbo has completely stopped spooling. Every now and then it will come back and the car runs normal, but most of the time the car runs like crap (reduced power up to 3.5K RPM, almost none above that).

Is there any chance that this is a diverter valve issue? The fact that the turbo comes back on-line occasionally gives me some hope that I won't be out $3,000 I don't have to resolve this. Or does it sound like the turbo is shot?

More Info:
When the turbo isn't working there is a prominent ticking sound at idle, about once every .5 seconds. It is similar to a valve tap but a bit more pronounced and a tad more metallic sounding. This sound is not present at idle when turbo is working. Giving the engine the slightest bit of gas makes the ticking stop - it does not increase with RPMs, it just goes away.

Are you stock?

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