1) the low speed needle determines how rich or lean it is between 0 and 50% throttle so leaner equals more acceleration and also will stay idling longer.
the best way to check the low speed needle is to get your car running rund the car in a circle or two, then bring it back to you and pinch the fuel line. if it takes longer than 5 seconds to died then it's too rich, if it takes less then 3 seconds to die then it is too lean.

2)sounds like your high speed needle is too lean and it's getting starved of gas when your going full throttle. set it back to factory settings, which is all the way in, but don't tighten it!!!!!, then 2 1/2 turns out. Then re- tune it.

3)the redcat site has something about tuning but also take a look at this
[link=http://www.youtube.com/watch?v=pEGjExP9GkM&feature=channel_page]http://www.youtube.com/watch?v=pEGjExP9GkM&feature=channel_page[/link]

edit: also make sure that your engine doesn't go over 260 degrees fahrenheit