See these advertised with the usual claims for improved throttle response etc. Do they make any significant difference (I have a 2.0 lpt 9-5) and how intrusive is the "whoooosh"?.

Saw one advertised second hand on e bay last week, by the time 2 guys got involved in a bidding battle it very nearly reached the price of a new one from PFS !

General advice is don't fit an atmospheric dump-valve (i.e., a whooshy one) to a Trionic Saab.

Lots more info about DV theory here:

http://dv.mistertam.com/

You would have to use a recirculating valve...