the charger was working fine before so no probs there and it's all connected up. i'll check the boost return valve but I reckon that's ok too. I don't have a boost gauge so not sure if there's little or no boost. I have found something which may be the problem, on the underside of the inlet manifold there are two "threaded holes" which don't have any bolts in them, should there be? At idle there is not obvious hissing sound.