You want a recirculating dv as a atmospheric will mess with fuel/air mixture and possibly cause engine damage.As far as type ,there's the bailey dv30,forge dv006 and hyperboost which are all piston type dv's that will have slower response to the stock diaphram dv although will have the benefit of more reliability especially when chipped ,ie more boost pressure.The forge model has a good reputation,failing that get 2 stock dv's (?18 each) and replace them if you feel any loss in performance due to tears in the diaphram.
