V10 TDI turbo boost won't work again

[kenchurch]

Hi, I own a V10TDI 2004 Touareg. I have had repeated problems with the turbo boost function. First and often repeated were problems with the turbo boost cutting out due to 'oxygen sensor lense clouding with oil and misc. This caused severe power loss. Next came the failure of a horse shoe clip on the exhaust gate starboard disconnecting the linkage. 5000 km later the other clip also failed. These clips are VERY expensive to replace taking some 4 hrs. to get at just to put in a new 5 cent clip.

Most recently the turbo boost failed again. After 3 visits to VW dealers all with the same diagnosis I took their advice and changed out the engine control module. That did not help but the 3 visits to diagnose and replace the module cost just over $2,000. Now I'm out $2,000 and my turbo boost still doesn't work! I have also lost faith in the repair process that I am loath to take the car in again. The last guy suggested that the computer suggested another remedy being to replace one of the turbo chargers ($4,500 + 15 hrs labour).

I asked if he could tell if the unit had failed or not reminding that the engine control unit didn't end up needing replacing but I had followed the computer diagnosis and done that. He went back and did more checking and found the horseshoe clip off on the port side of the exhaust gate. While this repair was obviously necessary it still did not correct the problem.

Final potential clue .....
The mechanic noted that there was an unusual amount of corrosion in the linkage for the exhaust gate.

Any suggestions???

Very frustrated, out a lot of money!!!