Boost leak check all ur pipes make sure none have blown off. Is there blue smoke? If so turbo. Is there any knocking? If so knock sensor has retarded timing, loads of possibilities start with boost leak
Glad u got it sorted matey. I had a slight leak tonight was driving along got to nearly.full boost and hisssssssssss proper loud. Knew straight away what happened, my mate didn't.do the boost pipe up proper the other day and it gave way, half hour later as I had no jack and was at side of the road, the cars working fine again, good job I carry a socket set with me