Injection Timing Valve Error 4422 - Strange!

Hello,

Since having my Audi 100 Type 44 2.5 TDI (engine 1T) washed (I'm wondering if there's a connection), I've been experiencing the following problem:
When the engine is warm (above 70 degrees Celsius), it roars loudly during startup (exceeding 2000 RPM), and then doesn't deliver its full power, estimated to be about 2/3 of its maximum. The turbo boost is missing, so I suspect that the boost pressure is being limited to a minimum by some kind of emergency program.
When the engine is cold, everything seems normal. Okay, maybe the engine sounds a bit rough, or it smokes more than it should, but that's rather subjective and could also be due to the high mileage (>250,000 km).
'Then I discovered a way to outsmart the electronics: if you remove the coolant temperature sensor when the engine is warm, start the car, and then plug it back in, everything works fine, just like with a cold start.'
The error code indicates a problem with the fuel injection start timing valve. This valve costs around 300 euros, and I don't want to replace it blindly, which is probably what the workshop would do...
I stopped using the fuel additive some time ago (approximately 5000 km ago).

Hat jemand irgendeinen Rat was ich machen kann? Thank you.
Bjoern.

Sure, here is the translation of the text from German to English:

'Explanation here:'
/viewtopic.php?p=6671#6671

Hi, Björn.