First off, I am jeff dunham, my best friend is Les Tinius of LTR... (so you know my bias).
From what Les has told me and in talking to other gasgas owners the LTR jetting kit works for most folks There is personal preference about how a bike should run, riding style and in what domain a person wants the bike to run cleanly. So talking about jetting is at times about as productive as discussing politics in a bar.
He told me has sold over 2500 jetting kits worldwide. They are sold through a variety of dealers and also on-line vendors (e.g.
www.gofasters.com). If you contact Les (e-mail or phone)- he will set you up with a needle and a set of jets specifically tailored for your bike, altitude and environmental conditions. And yes, it is a needle made by keihin specifically for this carb (numbers machined off to protect the innocent)...
He will also help you dial it in after you receive it. It costs $36 and includes support and consultation with Les to help get things "dialed in" (look
here for his qualifications).
I think it might be better to describe my experiences. What Les told me during the process, and what conclusions I drew from it all. This way you can seperate out my experiences from my conclusions and develop your own picture of the situation (and maybe factor in my bias too!). Then you can decide which way you want to go to dial in your jetting.
jeff