Aloha Palic,
Regarding backfire. With a vapor carb backfiring is a problem because as throttle is added the mixture can likely become too lean causing a backfire into the carb verses too rich which will cause a backfire into the exhaust. A backfire into the intake on a vapor carb set up can be an explosive event.
When I said try something else I was referring to possible duplicating of some of the projects shown on this site.
You asked if there was a better way. For me the simplest method showing the greatest results is the nitrogen based hydrogen booster posted on my project page and under the heading- mrgalleria- can you test the nickel again. This is such a new product, that it has not fully been investigated yet. It may prove to provide even better results than those to date, which show up to 50% improvement in run time on the same quantity of fuel while producing hydrogen gas from a catalyst and engine heat.
Bill