Z3 2.8 Cold tickover

[Daynsie]

Hi Folks, help appreciated, I have Z3 2.8, when started from cold, it fires and runs perfectly, if left to tick over it hesitates, tries to stall, and sometimes does, once driven, even only a very short distance, its fine, any ideas?

[Nat_H]

Oil separator?

[phelix]

Vanos seals - replacing them solved a similar problem on my E46 328i. See http://www.beisansystems.com/