Shire350, not sue if you have seen this thread but it sounds like your problem to me,
http://www.350z-uk.com/topic/99607-zed-owners-must-read-p0011-p0021-caused-by-oil-gallery-gaskets/
, sorry if I'm barking up the wrong tree (I'm just a Lurker).
If you dont mind me asking mate, whats the insurance like on that beast, I'm VERY interested. I've got a TT at the moment and just cant stop looking at 350's ))