Someone will who has intimate knowledge of the ST, I am a Cossieholic and don't own an ST, so don't know first hand.

As a tip if you don't have much luck here put a thread in 'General Car Related Discussion', as that gets more views, failing that there are bound to be some diagrams/info on the net, i.e. STOC.

Yes thats the diaphragm test, it sounds by the way your describe the sound now though, you may have bent valve(s), in which case this would concur with what your guy is telling you.

I should imagine it's like other Ford engines, or Volvo in this case, there are no timing marks to align, if so you should be able to locate 'TDC' be inserting a screwdriver etc into plug number one until it reaches the highest point, anyway you need proper information to do this as it's not something you want to mess with without the correct knowledge or tools.

Martin