Hi,
The cold weather thing is a problem that's been there from the beginning. It seems the OMVL ecu and the original engine ECU (Rover MEMS) just don't get along well. I've had a wideband lambda on the car and it's spot on when warmed up (14.7:1 AFR), but from a cold start in winter it's much leaner, once it gets to 21 or 22:1 it starts gentley missfiring (you can smell the unburnt gas) and the idle starts bouncing up and down as the MEMS ecu tries to stop it stalling - which it will do if it's bad.
Richening the mixture in the OMVLA software would make it richer at all temperatures, and MEMS seems to just use the lambda sensor to lean it back again to achieve 14.7:1 when warm.
The funny thing is that in very cold weather, even when the engine is fully warmed up (say, driven 5-10 miles) it can sometimes act up - jerky at low speed. It seems to be the temperature of the LPG tank that makes the difference. I keep meaning to compare the gas pressure in the software in summer Vs. winter.
As something of a bodge I wired a 5K pot in series with the engine coolant temperature sensor to give me a manual choke

It does help quite a lot for cold starts.
It puzzles me a little because LPG shouldn't need cold enrichment!
I'll certainly change the filters

I can't expect it work properly if it's gunked up!
Thanks again,
Ant