you have probably disconnected your blow off valve vacuum lines from the inlet manifold and the inlet pressure on boost is blowing the valves open at about 5 psi
You got my innuendo mate! These are tough little engines, they don't often die except from sheer old age, and there are well maintained NA's getting around happily with 400,000 K's on them as of last check. TT's maybe less so... The point is, you pretty much need to murder them to make them stop. I sincerely hope Michael Burton gets a good outcome. But I need to hear more about the head gasket business before I can offer any useful advice.