Its not very easy to do, you have to come off the throttle in such a way that the car drops boost but doesnt go into vacuum so the DV doesnt open.

Was coming back from weston last year with my mate in his R5 GTT, he had a T3 Roller on it and a Forge diaphram dump valve, and he was moaning he couldnt drive on the motorway without the turbo boosting (being a roller) so he was dabbing the throttle and realised he could make it chatter without the DV going off, and i joke you not i fell asleep and woke up about 3 quarters of an hour later and he was still still doing it with the same chuffed as fuck look on his face PMSL