Hey guys I have a AUII runs dedicated LPG tonight i started her up went to put my foot down hard and heard a pop from the back and then the car stalled i was able to turn it back on but yet when i would go past 45KM it would continue to pop and turn off.... any ideas...???

Lots!.

First - When it backfired, its likely that the inlet pipework got blown off of blown apart. You probably need to look under the bonnet and then connect/fix it back up so that the MAF or MAP sensors can read correctly. LPG also requires the restriction of the filter based on its tuning.

Second - You most likely need to replace your (spark) plugs. Backfiring is a common indicator that its time to replace them