RE:Someone help me out here Jetstar and the HG series are completely different. Jetstar was brown gas ( combined hydragen and oxagen gas mixture). The HG series separates the two gases completely and injects them separately into the engine. Also the HG series uses the smart ECU to change the flow rate to optimize the combustion.
There is no comparision between the two. Almost a decade ago, they scraped the jetstar program and started a new complete redesign which resulted in the HG series we have now. I do not believe there are any Jetstars still in circulation.