No power on petrol???

[vogue]

Hi, i have a '95 V8 on lpg.
I recently had a major backfire that destroyed the air box due to lpg (my fault, should have installed new dissy cap and rotor). All fixed now and runs great on gas but not on petrol. In neutral it revs freely and sounds normal, but in drive it won't get over 2000rpm on the flat and just dies on any small hill.
What could it be?
I have also just put in a new MAF.
Thanks

[bee utey]

Occasionally a LPG backfire on gas happens because the petrol isn't assisting the starting phase. So your petrol may have already been on the way out before the backfire? I would be looking at the fuel pump, fuel pressure at the rail when under load, perhaps time for a new petrol filter.

[vogue]

Well today i tried the cheapest thing, new fuel filter, no change.
Is there a way i can check the fuel pressure or should i leave that to my mechanic?

[bee utey]

Is there a way i can check the fuel pressure or should i leave that to my mechanic?

Dead easy, so long as you have a shed full of odd fittings, fuel hose, pressure gauges etc. Failing that it might be time for a visit to a LR mechanic...