can anyone tell me the correct way to clean out a boost solenoid on a 1995 impreza ?

 

I take it yours is an RA Same as mine.
Do an ecu reset by connecting the 2 black and 2 green plugs together (ignition off) that are under the steering collum. (ruffly level with your left knee) They might be rapped in tape if not used before.
Take off the pipes on the solenoid (the 2 on the side)
Turn the key (don't start engine)
Solenoid should start to click (quite loud)
Spray carb cleaner through it (some may splutter back)
With plugs still connected start the engine and drive for at least one minute, keeping road speed above 11km/h
At this point the check engine light should start to flash the all clear signal (steady 1/2 second interval flashes).
If the light does not flash or indicates some other sequence, there maybe a fault present in the system.
Stop the car and turn off engine.
Disconnect the plugs.

See how you go.
Worked for me