Just bought another Impreza after a long term away from them. 2002 wrx, standard boost.

The boost gauge fluctuates quite badly on full throttle, kind of surges?
Ive cleaned and changed boost solenoid, changed both lambdas with no effect.
I did tighten the actuator rod a turn which did help but after further tightening the problem was still there and got no better so I returned it back to one turn.

Any advice welcome

 

get it ona dyno and see whats what, could be a moded car returned to stock and the map isnt right