Something that may be relevant for gas users:
Our Zavoli system will always start on petrol, even when hot, and then switch over to gas, almost immediately if hot or as soon as things are up to temperature if cold.
We find that if we start on petrol deliberately, by selecting that rather than gas, and running it for a few miles, it does run better, even after switching to gas.
There is some interaction between the two control systems, the likes of which I have yet to fathom, but I get the feeling that very often a lot of faults could be cured by a good run on petrol, deliberately blocking out the gas side altogether.
We haven't tried any injector cleaner in the petrol yet, and always keep 3/4 tank of petrol at all times.
I read through the 'Hints' and found a lot of it to agree with, although it could do with a bit of an update now, still a good bit of work.
Peter