Well, it may not make loud noises but I have learned something very interesting about how the bypass valve works on my car.

Instead of operating off the total boost pressure and venting when it goes too high it has a much better method of managing boost pressure at the same time it improves turbo performance.

On my 930 the bypass valve works not just off the boost pressure but also the pressure difference between manifold pressure and boost pressure.

For this reason if the throttle is fairly closed but the turbo is trying to spool up it opens up so the turbo will encounter less resistance and spool up more quickly than it would if the flow was being blocked.

This bypassed flow is also fed back through the intercooler again which improves the thermal efficiency of the intercooler system.

I will post a pic of this strange piece of plumbing as soon as I have a chance.

Ah, the interesting things you can learn when taking your engine apart and looking over technical documentation.