I've just had my clutch replaced on the Impreza, and since then, my MY99 seems to have a strange boost issue.

The boost climbs normally, then suddenly spikes to 20 PSI before suddenly dropping to 10 PSI, then climbs back to the normal 16/17 PSI. This makes the car noticably surge and drop off! Very odd.

I've checked all the hoses, and nothing seems to be out of place. Someone suggested it was because the ECU was in 'learn' mode after the battery being off for several hours during the clutch install.

Any ideas? I'm stumped!