Just info on an experience to work just recently, My au2 has an omvl r90/e gas system. I was driving along and went to over take a car " while on gas " normally no worries. But his time.( I fast feed the throttle dont flat floor) When i did this , massive front fire. Car spluttered and started to die. DAMN DID I LOOK LIKE A TOOL. I switched back to petrol and went flying past the car infront. Then from there on rough drivng on gas and i could smell gas. car idled fine though..... I took a look under the bonnet and found one of the plugs to the duel out puts had come off and pulled half the diaphram inside. After replacing the plug and checking the diaphram for tears and placing back inside, It was back to normal.

EF, AU and BA onwards models with OMVL's are notorious for this. It's the s**t coil pack set up and plug combination.
Switch to an EL distributor and coil, ( will slot right in) if you can figure out the wiring or have a mate that's handy with wiring and it will half your problems. Other than that, call Brian at Newgas in Taren point NSW or speak to Michael at Rapid Flow in Hoppers crossing Victoria to get the right plugs, decent leads and check your coils. There are a few mods you can do to the omvl's to make them flow more and reduce the backfires but heavy acceleration on all the above models tends to do that with omvl

Never had that problem with an R90E on my AU. 0.9mm plug gap, decent leads and tune by someone who knows what they are doing will have it sorted.

The BA only does it when the plugs are getting on or some idiot leaves the 1.5mm gap plugs in when he does a conversion. Personally I think any installer that fits a venturi system to a BA needs to be shot anyway.

thanks for the info. Well apperciated. The gas input 'is directly infront of the thottle body'. Is there any benifits for moving it further back along the air intake to get a even mixture of gas and air????