Just an update, martain tracey told me he would put it down to leaking compression on a valve or piston ring, with the engine only rebuilt i was hoping it wasn't and the only thing i tought it could be to do this is the vtc removed is messing with the timing on low rpm so i stuck it back in along with a set of rocker arm stoppers and so far so good vacuum is back good and idling nice at 800-900rpm..

Thanks for the suggestions ppl

Bobby