Here are things to do before the conversion.
Make sure the engine is serviced and running to it's full potential on petrol. Change the oil, ignition components (see below) and coolant (if need be).
Get new spark plugs. Cheap ones are probably the best (read on for more details). Gap them to 0.8mm (this is
vitally important for best driveability and economy with mixer-based gas systems). Even though they typically last longer, iridium plugs aren't recommended as they cannot safely be re-gapped and it is easy to forget when you originally installed them (bad!!!). Replace them every 10,000-15,000km and you should rarely experience a backfire. At $2 a plug or so, standard spark plugs are definitely best value. Stick to known brands such as NGK for best results.
Get new ignition leads and make sure your ignition coil(s) are in top condition. Anything less than optimal will potentially cause a backfire. Remember, a gas engine relies on a strong ignition system.
If needed, replace the oxygen sensor(s). A properly functioning oxygen sensor can mean the difference between acceptable and unacceptable fuel consumption and performance.
Make sure the gas system is tuned every year or so (again to minimise the chances of problems). It is good practise to get a gas tune done immediately after an engine service.
Other than that, enjoy the cheap motoring.
Regards,
Dave
