Please help, before i kill my car!!!

[amiers]

A little back ground first. my car is an AU2 5L dual fuel Fairlane. i have owned the car for 4 years and 100.000 k's. when i bought it i did the plugs/leads ect it has never missed a beat on petrol or gas in that time.

fast forward to 3 weeks ago, lpg converter failed. booked it in for next week. gas guy asked to make sure car was running right on petrol. so i thought it was about time for some plugs and stuff. asked what plugs he thought were best, NGK BPR6EFS was the answer. i took out my plugs, they were just about stuffed, they were BPR5EFS-13. and now it all went south!!!!!! Put in the new plugs, car wouldnt idle, drove fine but wouldnt idle. put a post in the lpg forum and general thought was 0.8 gap was too small, rang gas guy, he said try 1mm gap. did that idle better but still lower than should be, reset ecu, now idle rising and falling. rang gas guy, go to 1.1 gap. at this point i checked the gap on my old plugs allowing for wear, about 1.1

so set the gap at 1.1 idle better but still too low but steady, took it for drive idle now rising and falling again. so one minute i have a car that runs smooth as, i change the plugs and it does this!!!!! so is it the lower heat range,6, and the plugs are fouling at idle? or is it the gap? With the BPR5EFS-13 the car ran perfecty on gas and petrol. i checked the ics it seems ok but when i unplugged it nothing happened? could it have all of a sudden gone dead? before the new plugs went in the idle always ajusted itself when the air came on or i put it drive now nothing. i have checked all the vacum lines and anything else i might have bumped


please any idea's