Turbo spinning but no boost

Hi I have a 1995 Impretza STI. I left it into a garage to get the exhaust refitted properly and when I got the car back it would not boost properly. As soon as the boost was due to cut in you could here a loud swish noise like air been dumped and no power. The car would miss and mess about. I could drive the car as normal but as soon as I put the foot down you could hear the air and no boost.

I took off the intake manifold and re fitted all the air pipe plumbing and checked all pipework to and from the intercooler for leaks and all is fine. I took it for a spin this evening and the the same problem was hapening but ot as bad. Then a small pop and no boost at all. Just driving like a stock non turbo. I took off the intake pipe to the turbo and started the car to see if the turbine was still spinning and it is.

Im lost as to what the problem might be. I am going to try and dissconnect the EVC in the morning to not allow the waste gate to open to see if it is a faulty controller.

Anybody come across this before??