I forgot to mention that it has never run perfect, before i started working on her, it used to overboost, it would start boosting and then get to a certain point then either cut out, or just splutter, but sometimes if i accellerated slowly it would boost alot better, I am wondering if that AMAL valve if plugged up correctly, as i was hanging off when i first bought it, is there somewhere i can find a diagram of how it plugs in?..

Tonight i am going to take the inlet manifold off and see what is making that hissing noise.. I had a look behind it yesterday when it was running for a couple of mins, and it seems to be coming from that large black plastic pipe in the middle behind the inlet manifold, .. i tightened the jubilee clip up as much as possible but its still the same, i think im better off removing the inlet and having a proper look,
Thanks for the replies so far, il let you know how i get on.. By the way if anyone else still has any ideas please let me know..