Firstly, when using light throttle to maintain a steady speed, it will somtimes lurch, and "kangaroo" despite a steady foot.
Secondly, there is an intermittent acceleration problem on LPG.
When I first bought it, it would not accelerate well on LPG - the power was coming in "surges".
I replaced the plugs, and instantly it was much much much better.
But now, the surging while accelerating is back intermittently (although nowhere near as bad as before).
The evaporator is red hot, no smell of LPG, filter recently changed, and no fault codes.
I am beginning to think that maybe the coil pack is a little tired - hence OK on petrol, and intermittent on gas?
The only other observation is that this car seems to have 2 lambdas. One in the top of the manifold - and another behind the exhaust flex joint.
The exhaust flex join has a SMALL blow which I've just noticed - I wonder if this is potentially confusing lambda readings and causing the problems?
It is very small though.
The problem is much more noticable on LPG, not really apparent on petrol.
I don't think it's a LPG system fault though - I think it's an engine issue, which is just being shown because LPG places higher demands on ignition components etc....
Any thoughts most welcome