Had a kangaroo experience recently on petrol. Car (2004 v8 petrol) starts fine on petrol from cold and runs up to 2000 revs but on pushing accelerator it goes very lumpy and coughs and farts but will go up to 4000 revs and then stop.

Runs 100% on lpg

Waiting to get codes read but in the meantime:

Is this
A) injector fault
B) fuel pump (fuel obviously getting through to engine as it runs fine at idle)
C) air prob (unlikely as it runs at low revs?)
D)other?

Thx
DB