When I took my car to the LPG mechanic over a year ago he reckoned me ECU was stuffed. Reason being is that on either fuel revs sometimes - quite often hunt when idling. Usually it's only 100 to 300 difference in hunting (e.g. the revs might range from 600 to 800 and slowly go back and forth).
Anyways, I left it at that drove the car around, and next time I went back (over 6 months ago and I think the converter bust and I had a new one fitted and that) he said the problem was still there and that it's not the ECU, it's actually the idle plates cracked. So anyone wanna tell me about this? I can't seem to see anything cracked on or around the throttle body, and there's no way I'm paying anyone else to fix it.
It's not a high priority - as you can tell, but it's just another thing I'd like to get fixed! By the way, it's definately not the ECU as I just fitted an EF Tickford XR6 one and it's still there. The cars auto but that should make much of a difference.

you could spray some WD or carb cleaner around the effected area and see how badly it does affects idle/revs. If theres a vacuum leak it should. would give some indication if that was the area of concern.
How does it rev (once warm) with the iac disconnected?

You could consider also that a bad earth could have an affect on idle. I'm currently experiencing that now on the windscreen fan motor, whenever its running. Perhaps conduct your diagnostics with all sundry devices turned off. It obviously wouldn't be playing up when the second thermo kicks in?

mmm ssounds liek it could be the ISC

If you turn idle up alittle does it make any difference ?
Disconnect isc adjust idle then reconnect isc...[idle speed control] has any names..Like iac etc...

I've cleaned out the ISC. Playing with the idle doesn't fix it.
Sometimes, very rarely after some spirited driving, I'll get home and put the car into neutral while getting out the garage door remote before putting it into reverse and the car'll start reving it's self up a bit and sit at around 2,000rpm.
I've recently changed the MAP sensor aswell, didn't effect it.

The thing is that it's not all the time that it hunts and that - it does it every time the cars started now, but that's only started sinc ehte new cam and goes aay pretty quickly. Then most traffic lights and stand stills it's fine, but a lot of them it'll hunt a little.