I play with a lot of european diesels and I love the VW 6 cyl diesels but those suckers are a iron block, al head combo with MLS head gasket and TTY head bolts torqued down so tight it will have you cryin for mama when you hear the noises stuff starts making when you either go to tighten one down or take one apart
You generally only hear those kind of noises on big Cat engines, and usually not as bad, but those little VW engines are squeezed together TIGHT and that aluminum starts to flexing and squeeking like you wouldnt believe when pulling those bolts all the way down . They have about the same compresin as an IDI but commonly see boost numbers around 21,22 psi.
The things run great, but have zero tolerance for overheat ( main reason I found Evans Coolant , no more of THOSE expensive little problems, last nasty little pre Evans incident involving overheat and thermostat a long way from home cost me thousands)