Many older turbocharged cars also didn't come with intercoolers, then there is CIS, etc, etc. That really doesn't mean anything in and of itself. At the time most of those cars were built, turbocharging was in it's infancy with gasoline automobiles. Even at low pressure it is still entirely possible and actually more likely (lower than WG spring pressure that is) that you will see compressor surge. At the moment I'm only running 7psi on my Carrera temporarily and I still see surge at partial throttle and building boost pressure below the WG spring pressure. I've seen the same thing on my 951 running around the same boost, so it's not just high boost applications that will cause it. If you are running less boost pressure than the WG spring pressure (such as in partial throttle conditions) all of that pressure has to go somewhere unless you have some way to release it. My 60-1 is dying a slow death because of it.
Oh well, it's just an excuse to upgrade.
Patkeefe, rubber in your intake (unless there's maybe a bellows/accordion style intake pipe somewhere) isn't going to absorb all or much of the backpressure and you are still likely to see compressor surge.
Just FYI but those plastic bosch BV's aren't all that great. With greater than 14psi they tend to leak pretty badly. Also, over time, due to the relatively light spring rate inside of them they can start to leak which will cause slower boost response. IMO, it's not even worth messing with them when you can just buy a billet BV or aftermarket BV/BOV and have a better unit.