Ford Escort RS Turbo

Ive just gone out and brought my 1st rs turbo cab it was well worth the money(or so i thought) on my way home the car kept cutting out wen i came to a juction or at low revs and also there is a slight knocking noise comeing from the engine,ive also found out that the head gasket has gone thats why the water keeps disaprering when i go round the block!!
< br/ > any 1 with any answers as to the noise or cutting out problem please HELP
< br/ > cheers Matt