AU I Xr6 LPG problem

[tacticz]

hey guys,

started my car yesterday morning, running on empty (gas), slowly got to servo, filled the gas tank up, went to leave the servo, as i accelerated car started to backfire sounded like through the intake air box, now the car hardly idles on gas and soon as u put your foot down backfires through air box, switched it over to petrol idles 90 percent alright, but sort of stumbles under hardish acceleration,and idles high on petrol, the gas sytem brand is impco, i turned up the idle on the gas system little screw thing on the left hand side,just wondering if anyone may know or had this problem before.

thanks.
Dan