Some has sed it could be the headgasket if it was pressurising the oil galleries tho it tends to pop the waterways on cvh gaskets
Iv had the head off cuz i had a race cam in but it was s**t so i popped the old one back in and it ran alot better.
So im going down to ford to get one and ill see from there.
Pete.
Ps,Ill let you know how I get on