Outer Limits 4x4 Board

Hi All,
I have a new to me 89 GQ TB42 on pet and gas, sucker ran grouse on petty, after running gas for a few days she wont idle on petrol now.
I have checked to obvious but to no avail.
Any ideas?
Its like the idle circuit is blocked in the carb, it will run above 1000rpm fine, and on choke.
Any help appriciated.

i had the same prob ran great on petty for the first month i had it then went to s#$t and only ran on gas. i had the carbie re-kitted(as the gas drys out the seals) and a tune done new plugs and points and runs great on both again.