Car was running a dream and boost was down quite low at 6psi. Had it in garage for MOT, it got some welding and now theyve dropped it off the car runs fine but no boost pressure.

when the engines started the vacuum gauge goes down to -20psi and under load the needle returns to 0

the dump valve moves in and out when revving the car stationary

checked the shaft and that spins freely

checked the pipes to and from the AMAL valve

checked the actuator arm for damage

Just looking for advice on where and what to look at as the cowboys at the garage stung me for £450 to weld my car and now theyve f*cked it they dont want any involvement! So now im skint and without my car.

Cheers for any help guys!

 

Have you checked all the boost pipes ? Mine s1 had the same symptoms and turned out to be the top boost pipe to the intercooler had just blown off whilst boosting hard !

 

Yeah i did look round at them all, i couldnt see anything out of place or cracked but ill check again over the weekend. There was welding done in the engine bay near to some wiring and the pink relay. I cant see any damaged wires but would that cause this problem anyway?