A 340 with single point normally aspirated LPG. Been brilliant for economy for a number of reasons - more range per fill, half the cost of petrol and less need to change engine oil (hardly bother now). But we have been bugged by poor idle - sometimes cutting out when decelerating. That isn't entirely sorted but the lack of power issues were seen to by using smaller gap plugs - 0.7mm as you suggested. This has improved fuel economy too - as there is a better burn, there is more power so less need to put the throttle down so far.
So your suggestion was a win all round. Thank you again.

Out of interest what is the reason LPG runs poor on multi point plugs?

Hope all is working ok now?

No worries, as said watch the coil-packs too. Expect them to go at some point. Petrol will be more tolerant with an iffy one, gas won't. If one is going AWOL pull the plug on each one until you DON"T detect a change.

Denso K20TT, simple one electrode spark plug with the factory gap and works perfect.

Before that, there were Bosch triple electrode spark plugs inside, I bought the car with them and also had no problems.

I have also heard that for CNG and LPG, singe electrode spark plug is preferred.

In short LPG/CNG is a different fuel. It require a different mindset to use well. For whatever reason, buyers seem to be happy to see the differences and account for these with EV, and not with LPG.

If the first EVs had been converted on the cheap from petrol, by people under rail-arches, and used by those too idle to understand the differences, we'd be hearing mutterings of how bad EVs are too.

Instead, it appears they've broadly won. LPG is set to wither on the vine. And because EVs are green at the exhaust pipe, we're told they're green. Are they actually any greener? The car itself is all 'orrible toxic metals mined in places controlled by the Chinese. On this they're worse, and a lot worse.

My point hardly matters, we're getting them anyway.