Are the diaphragms avialable for the wastgate or if not, does anyone know of a suitable replacement for the wastegate. I have no control over the boost, goes right round the dial if i am not light on the gas pedal.
Before replacing anything have you tested your wastegate? I think it's a simple test. Don't recall the exact numbers but something like 10psi pressure to move the actuator rod a short distance (would need to check the service manual for actual spec).
Pull the wastegate cap (use longer screws to let off the spring pressure) and make sure the valve moves freely. Many of these have stuck in the guide, preventing the diaphragm from doing it's job. I was able to free it up on the car with some penetrant mixed with high temp anti-sieze.
If it's not stuck, you are all ready to insert the new diaphragm!