V8 AU Fairlane not running when hot Heeeeelp Pleeeeease!!

[GTLexus]

OK, I have looked on the search function, and on the forums and to no avail.

This is the issue

I have a 99 AU V8 Fairlane on dual fuel with 199000kms.

It was running rough at idle on both petrol and LPG and then when accelerating it would not want to accelerate and run even rougher. The idle is that bad that the whole car shakes.

I replaced the coil packs, spark plugs, and ignition leads.

Cleaned K&N airfilter
Checked wiring connections on engine
Cleaned throttle body
Cleaned contacts to airflow meter
Changed oil and filter while I was there
Changed fuel filter

After all this the car still idled roughly and I took it for a drive and the acceleration was like it was still misfiring. I ran it on both petrol and LPG and it had the same symptons. When I got back in the driveway the car temp was at normal. I shut the car off and when I went to start it, it did not want to fire. I rechecked the leads and connections and they were all OK, out of desperation I gave the airflow meter a tap and the car started. It idled roughly and was backfiring.

It seems the hotter the car gets the worse it becomes.

Does anyone have any idea what to do next?? I have had the car towed to 2 mechanics and both of them could not find anything wrong with it