200Q 20vT + VAG-COM = Driveability problems?

[Kneale Brownson]

Taking this to the 200q20v list for more experience.
   
  In reply to Huw, there indeed are more complicated controls of the wastegate, including the waste gate frequency valve and turbo bypass valve, along with input from the ECU and from the various sensors on the engine.

Huw Powell <audi at humanspeakers.com> wrote:
  
> Had a little issue on a 200q 20vT this morning, so I plugged in the 
> VAG-Com to take it for a spin and watch the data. Trouble is that the 
> car was barely driveable, kept hitting the overboost cut out and 
> overall running like sh!t.

Is it actually overboosting? Your wastegate may be stuck closed. Tons 
of power, but too much. Mine (on an 83 5kt) used to freeze shut on 
really cold mornings, for just a few seconds. Wheee, 0-60 at 2-2.5 bar 
was fun.

That wastegate eventually was stuck closed for a while, very difficult 
to drive and then stuck open, making the car a bit of a dog.

> Funny enough after unplugging the VAG-Com and cycling the key the car 
> ran perfect - the issue I was trying to diag went completely away.

Interesting. Now, on your car, the wastegate is controlled by "things" 
other than simple exhaust pressure, right? Could one of them be sticking?