The only mod that I have heard of, for the Titan (Hua Sheng), is the Flexible exhaust pipe used on the EZ Motorbike, prototype. noticable prformance improvement has been reported.
With no mods this engine pulls me way faster, than I need to go, and I weigh 290 lbs.
The best change that i can recomend is the ability to use multiple speeds to improve hill climbing.
oldieone