what people are not understanding with a DV is most of the time they are for cars with slightly uprated boost.
For example car X is running a run of the mill DV valve and Car B has a HKS SSQV with the ability to compress the Dv spring.
Now when most people think there cars are having issues with DV most people immediately think its the Dv fault and change back, however this is not the case, i found out first hand while working on my mates EVO 6 that a spring can make the difference between **** acceleration and jerkiness to swift gear changes.
Now car X run of the mill Dv does not have the ability to change the spring (early baileys didnt ) and as such due to running more boost than standard the Dv is staying open during idle as there is more pressure, causing a idle surge and back acceleration.
Now car B, has just had a remap and is now running more power but due to the ability to compress the spring, a swift change is made and as such it now closes correctly.
do not be put of by the scaremongers or people that say your car will blow up etc, use a proper brand ( ive had baileys, forge , HKS) all have had no issues at all, if your turbo has steel internals e.g IHI or a ceramic internals, DO NOT run without a recirc or a DV as the added load of the turbo spinning backwards during gear changes ( chatter) will cause the shaft to break.
On my mates Tial on his evo the spring is colored and a simple equation is used to work out the spring that you need, once this was sorted he no longer had a boost spike, not all DV have the ability to change springs.
Cheers for reading.