My 4.0 litre v8 has werid idiol it starts from cold at approx 1500rpm then starts to drop to 1000rpm as the engine warms up .it drops right down near the mark just above the zero on the rev counter .and noticed only goes lumpy below 800rpm
Ive so far changed .lamdas.maf.coolant sensor.plugs ht leads.poitensionor metre.steper idiol motor. No fault codes and all new gaskets on the inlet with new vacume reg and pipes .anyone any ideas.

Next mine has the brc genius max system but is very poor on gas ( 68) mile on 20.00 before it beeps then changes back to petrol.ive changed gas filter .im thinking maybe something on the tank side as the led gauge never seems to move from 1

Disconnect the LPG system - pull the fuse, get the e u adaptions reset and then run it around on petrol for a while then see how she is. My money is on a poorly setup LPG system throwing your trims right out to the max.