baldrickbluescoob

OK long story ( u may have read other posts )
93 WRX was running 1.4BAR boost, but as i didn't want to melt the stock engine reduced it back to std .8BAR which was fine.
Now i have a problem, under acceleration as the boost gets to about .7 bar the car starts to splutter and the boost guage shows the boost 'bouncing' up and down. When this happens i can here what sounds like a solenoid clicking ( boost soenoid?)
was told that if (very temp.) removed pipe from soilenoid to actuator and did i test run - if boost problem went away then the solenoid was fautly - But it was still the same.
Have checked all pipes for splits etc - all fine
Dump valve is not sounding as it used too either - tried different one - still the same.
Ecu error codes show Oxygen sensor fault - would a fuelling issue cause this problem?

If anybody can help pls contact - it driving me round the bend
And I think my backup car may be sold tomorrow(if the guy turns up!)