4.4 V8 2002 Vogue missfire problem, gas converted

Hi, my 2002 Range Rover Auto V8 which we got converted to Autogas has developed a misfire. I left it into Hurst in Belfast several week's ago (Big Mistake)
to get it sorted, not sorted. So after re-finance the vehicle to cover the bill LOL! I went on Youtube & seem's a common fault with that BMW engine, anyway I am going to describe as best I can here in case there is something else needs investigated.
When driving along I can feel a misfire, very slight most of the time but occasionally it goes rough, it's nearly like one cylinder miss then perhaps a second ? anyway you notice it more on load say going up a hill, it happen's on petrol AND Gas, no particular time, I get the impression it's worse when warn than cold, a while back there was a fault that after cornering hard (part time fire man so that happens a lot !!) the engine light would come on, I would slip it back onto Petrol and it would clear, left into get Gas serviced, they said there was dirt in or near injectors ? any way it ran fine except for the hint of this misfire, now it seem's to be getting worse, no engine light on though, there is a really steep hill in Castlewellan which it is very evident on, it's also low on power on that hill on gas or petrol except when you floor it but in a 30 zone that's not clever !
Hurst test drove but could not feel the misfire, I can as I drive every day & know my own yoke, sometimes when sitting in traffic I can feel the revs dropping off and a wee shudder then it's returns to normal tick over.
So, all typed out now ! any ideas.

Is it like driving over a cattle grid??

If so could be the gearbox Lock Up Clutch....particularly evident on light throttle up hill at between 30-50mph....

The LUC limits Torque Convertor Slippage but the friction material wears out causing a juddering as the LUC trys to limit the TQ slippage....

Common problem on the ZF box whereas the GM box just lets go and trashes the Gearbox!!

Hi, thank's for reply, sound's like big trouble, though it's not like a cattle grid to be fair, more like a slight miss, the way an old yoke might go when distributor cap was ever so slightly out of place if you get my meaning, now it seems to be doing in on level ground also now and also it's def getting worse.
Is there any way of being sure about the LUC, like free wheel or ?

This is a great place for info, the guys helped me out
An easy thing to check, cuz I had this problem, but a lot worse than your sounds for the last few weeks.
Although may be completely different.
Check your wiring and connections to the injectors, I took the injector junction box covers off and mine was like a birds nest where they had chopped into the injector circuit to get the feed for the sequence for the LPG injection

Anyway I plugged mine into my compute and it said I had an injector fault and misfire in cylinder 2.

Found wires just twisted together! So I reterminated everything and it's now all sweet

Hope you get sorted mate!

Has anyone sniff tested this engine for headgasket?

On petrols, it's the first thing i do now.

I'm with saint. I spent six months trying to track down my slight misfire only to eventually discover it was the torque converter. Your symptoms are identical to mine. Try driving it in sport mode to see if it changes things and look for a wander in the revs at a steady 40 - 50 mph

Hmm, the Torque Converter was supposed to have been replaced there a few thousand miles back when the gearbox was repaired, it have a fault with reverse gear and near £4,000.00 leter it was going great, hate to think it's gone again already !

Yes I had heard the head's give a bit of bother also.

Discovered there was a leak in the radiator which has been cured by firing a new one in today

Hmm, the Torque Converter was supposed to have been replaced there a few thousand miles back when the gearbox was repaired, it have a fault with reverse gear and near £4,000.00 later it was going great, hate to think it's gone again already !