91 200 Q 20v Turbo Cuts power when WOT under boost

[90 Coupe Q]

I'm new here. my name is Ernan, i live in Portland, OR USA (born and raised in Bosnia, Europe)
I just bought 91 200 Q 20v turbo 5 speed sedan with 226k miles.
For some strange reason, when i start boosting under WOT 3/4 and up of gas pedal, something past 2500rpms engine hesitate and lose all power, looks like you hit rpm limitter, but if i dont hammered all way down i could get to 7000rps, it also reving find on idle but thats because turbo is not making whole a lot of boost since there is no load, also if i disconnect battery for min or two, hok up battery and take for a spin, it will go fine under boost and WOT for a few runs and it will start acting up
I have pulled spark plugs, they all working, little bit on lean side but not much its still gray color
So to me it looks like ECU is pulling timing, cutting fuel since i hear pining
Meybe is one of sensors, TPS, Crank, of cam shaft sensor, or even knock sensor if this Audi have one

BTW after i gat 200 running, engine/tranny will be swapped into my 90 Coupe Quattro
Im sorry for my english, it bad i know :)

[maynardGK]

I had same problem w/ '89 200 turbo: full throttle invoked engine shutdown for 2-5 seconds.
The mechanic found that the tubocharger wastegate diaphram was broken, he found the part for $150. From what I understand, this fault was also affecting the low-throttle operation, stressing the intake and possibly leading to head gasket problems, by allowing too high a pressure at nominal operation.

[scotty33]

Hi some good information on this site:

http://www.sjmautotechnik.com/trouble_shooting/20vboost.html

suggest you start by reading the ECU fault codes?