whats the diffirence between a re-circulating one and a atmospheric one? any y have two types?

 

Yep. The oem DV is a recirc type and allows the already metered air to stay within the sytem. A vent to atmosphere type will do exactly that, vent to atmosphere, and may need setting up with a possible change in fuelling as the ECU would expect the surplus air to still be present. Overfuelling if I am correct.

Have a look here for alot more info from the big boys.

http://bbs.scoobynet.co.uk/showthread.php?t=385353