During a cold start. If I push the gas pedal slightly (about 2mm down) and let off, just blipping the throttle, you hear the turbo (Not sure what it is) go pshhhhhhhhhhhh... and stop. Even when I am off the gas, It holds that sound for about 2 seconds afterwards. Is this normal? It's been doing it for a while now, I think its a cool sound but I'm not sure if I should be concerned about it.

2013 Cooper S Hatch, M/T, Intake, Exhaust

 

The factory DV is electronically controled, Meaning that the ECU tells it when to open and close. This could be the ECU holding the DV open. Normally there will be a delay from when you let off the gas to when the DV opens this could also be the culprit. It would probably be worth checking to see if the DV is damaged as this is pretty common. If you remove your turbo inlet hose there will be three allen head screws to pop it off. There are a few DIY's on here I think.