Thanks for your help to everyone who has replied.
I went back and sprayed brake cleaner all over the hoses and all around the manifold and it didnt make a difference but surely if there is an air leak then the revs would have risen. I tugged all related hoses and wiggled the temp sensor and all seems fine. Could this be a TPS stuck in full throttle possition? why does the revs drop from 6000 to 2500 when I dissconect the ISCV?