it drops to, at a guess (cos the guage is in bar!) four or five psi! not good! keep racking my brains thinking im a retard, but with the sump off its all in order and had no wee bolts left. anything in the head that could cause it to drop so much. its got a piper 285 t2. like i said it was perfect before so dont think the head could be an issue. got a wee skim to make sure it seated right but cleaned all the swarf off! tomorrow i think ill disconnect the turbo and try it but not holding any hopes up for it cos its a good turbo. think my brain may explode soon. this was a one week rebuild,a month down the line!!!!!!!