i have a 2wd cossy saph it is running 4psi of boost runs fine but when i try and turn it up it will only give me 6psi and it hesitates and backfires as if its overboosting i have changed boost hoses taken turbo and actuator off to be checked all came back ok switched amal valve and fitted diferent boost gauge still doing same thing any ideas would be greatfull as i am very close to torching the thing cheers