scooby96wrx

Hi have had a look at some posts and was wondering if any of you guys could help.
I have a 1996wrx import.has full blitz turbo back k&n induction filter forge dunpvalve that's about it engine mods.the issue I am haveing is the car has had boost problems for the last 7/8 months but it would only happen now and again ice once a week or not for 2 weeks but as from Friday its been there most of the time.my car normally hits 10psi and hold there but the problem is it is only hitting 5/6psi you can feel the car is holding back on boost but if you drive at say 50mph and at around 3000 revs then put your foot down the boost goes to 5 psi then hold then all of. Sudden it feels like it is let loose and hits the normal 10osi is it something sticking checked all pipes etc not leaking and changed dump valve back to the old one and still the same it has been a lot worse the last 3 days,
Could it be a sticking actuator and now its just got to bad or poss a boost solenoid

Thank you for reading I tryed my best to explain it as best I could,
Any help would be most appreciated thank again

Mark.