I had a 1995 T4 Lexcen sedan (rebadged VS commo) Best car I ever owned with few problems. I fitted LPG and it saved me a lot in fuel but kept backfiring. A guy I knew online from Perth told me about a taxi driver who ran a Commodore taxi with spark plugs gapped to 0.8mm which he claimed eliminated this common problem with the 3800 V6 on gas.
I did it to mine and presto, it never back fired again, plus it had much better throttle response. It's a shame I crashed it 9 months later.
