saff cosworth 2wd.400bhp greys, low comp running t35@32psi... recent full rebuild. head has been skimmed and new cometic multi layer gasket fitted. the car pressurise as soon as you bring it on boost. if you drive it out of the turbo it will drive for miles without pressurising but as soon as the boost comes in, even just 2 or 3psi it pressurises almost instantly regardless if car is hot or cold?? i have removed thermostat and it still does it but temp guage sits at half way (ok) rather than getting hot.

i have removed the head and had it checked for flatness. it is ok and DOESNT need skimmed. there is no sign of blow by on the head gasket and i have had the block and head checked for cracks using dye. both appere to be fine?? the only noticable thing is corrosion around the water jackets but it looks as if this is not realy where the gasket sits?

i am 100% sure there is no blockage in the coolant system and is defos a engine related problem.
has anybody had bother with these multi layer metal gaskets? or any unusuall head problems?? does anybody no how far you can skimm a cossy head (early 2wd) or even better have a good one for sale or re-con them??
any help appreciated
ps. i have bled the system properly and with a pressure bleader and there IS exhaust gasses getting into the coolant system