Hi,
Well, I started off with an abbott (forge) atmospheric dump valve, all worked just fine, however, I got an air induction noise in my JR filter/air intake tube in my front wing, which sounded like a wheel spun by a hamster, it wasnt the noise of the dump valve or the turbo blades stalling, just purely an air reverb in the tubing.
I then replaced this with the abbott (forge) recirc type and all was fine.
I have since changed my induction system completely, having a mesh air filter under the bonnet (with intake ducting under the front bumper). I have now reverted back to an atmos d/v (bailey twin piston) and I get the nice whoosh noise and no air reverb noise.
I dont experience any problems at idle either.
I know some claim a performance difference (2bhp) by fitting a higher spec valve, to be honest I have not noticed and increase in power, no a reduced spool up time.
However this could all be down to the fact that I carried out other upgrades at the same time
Hope this helps!