I have never even stripped out or cracked 11mm bolts when reusing the stock bolts
and have put a VNT-15 with the vanes locked closed on a 1.5L block with ARP headstuds.
Boosted to 35 with the great backpressure of a VNT working against it,.. a couple times. With no adverse effects.
Sidenote: I replaced the stock headbolts 1 at a time withy ARP headstuds and was worried it might leak but it worked great.
My TD Golf by comparison has 12mm raceware headstuds ,... oil seeping from the front and I retorqued them after seeing coolant coming up around the threads of a stud.
I think Andrew just got a bad 11mm block.
i boosted up to 35 many a time..
its not till i boosted it up and left it there for a mile or so, that it popped..
popped somewhere north of 40psi.. 30psi is at like 4'oclock on my gauge, well, i had it almost wrapped back to the 0 peg.. lol.
blew a chunk clear out of the head gasket..
and the #4 end of the block was TRASHED..