The car is a stock dual fuel XF Falcon 4.1L Auto

stalls straight away when cold and idles really low/rough and takes like 5 times to get it started too.
I've replaced the fuel filter and fuel pump.

Here's what I noticed if I slightly close the choke butterfly when warm while engine is roughly idling on petrol it idles better
To me its running lean then, but the mixture screw is 2 1/2 turns out I even tried richening the mixture and it didnt make a difference on the idle.
I couldnt even drive it on petrol as it stalls if I let go of the accelerator pedal.
I tried advancing the timing and made no difference.

it drives good on LPG

Any ideas?

your going to need a reco carby mate
or even a new one depending on your budget.

grandpa's XF did the same thing. also a 4.1 but it was 'efi'

Would love to know whats causing it when you fix it

It could be your vacum sensor on the firewall, unhook all the vacum lines with engine running and attach them one at a time and when it cut s engine revs, thats the one that not working properly. I spent $5000 on trying to get mine to run properly. Unhhooked the vacum lines to sensor and it even starts on gas now. The car sounds/ run A1 now after all the workshops and mechanics told me I need this and that, new this and that. Easy to fix. Moreton.