Mark,

Can't be the fuel regulator as I've mentioned this has been changed. Problem occurred both with standard and also with fse regulator.

Costina,

Think I've finally caught your drift...the top pipe from the swirl pot (see below) returns to the tank....but no vent from swirl pot!

http://www.rallydesign.co.uk/popup_image.php?pID=11750

Planning to T piece in a pipe to vent together with one way rollover valve as high up as i can. Will do when i'm allowed in the garage again after this weekends time spent and trackday on monday!

this is the only thing unchecked that could influence IMO. Thanks for your help. I owe u beer vouchers if this sorts it!