lpg v8 problem

Can anyone shine a light on this, my v8 90 which is running on lpg, sometimes backfires, or when it is going along at about 50/60 mph it seems like it has no power or looses power, when i pull over to the side of the road & rev the engine everything is normal, put it into gear drives normally. i am at a loss as this is a intermittent fault that just pops up.

Possible vapouriser problem?

Is it a Single point or multipoint system?

Its a single point. cheers

worth checking / servicing the distributor too

compression test-if it has started to go between cylinders on HG.

Also check vaporizer not freezing

Hi i found & sorted the problem, it had a split in air filter hose, bit embarressed really, but cheers for the replys