Over the weekend (in between the rain) decided to change from the open circuit dump valve back to recirculating one to see the effects.

Apart from losing the cool/annoying (depending on mood) sounds beloved of Max Power readers I've notice more boost is retained on gear changes, a good 1/4, 1/3 orange boost is registered imediately on reopening the throttle, and more importantly it seems easier and smoother when feathering the throttle when driving Welsh B roads.

Strangely the atmospheric dump valve makes a completely different noise fitted to my friends 9000 compared to my 900.

Interesting stuff. What dump valve have u got as im in the process of upgrading my car.

The atmospheric dump valve that I've currently removed was a Bailey Evo DV26. Replaced at the moment with a Group A spec item that I purchased from Turbo Dynamics several years ago featuring an aluminium body and kevlar diaphragm.

The valves made by Forge (www.forgemotorsport.co.uk) have a very good reputation for build quality.

These are the people that make the Trent Saab uprated wastegate actuator for the TE05 turbos.

Yeah I'm thinking aboutu putting another blow off valve on my 900T spg. I hear they keep the turbo spooled up. Is that true. Also that release nosie is kind of cool, but I could see how that would get annoying. Why doesn't my car make that sound now? Any suggestions on a good valve to get and where?