I have only been runnig petrol/gas for a year or so, which makes me a newcomer as well, but it sounds like you are lean on the top end, the low mix screw is working all the way through the rpm range and the high kicks in at around 1/2 (I think) You have a tuning problem for sure, my dle's have never dead sticked at all, use a plug in rcexel tachometer when you are tuning, I found the optical ones are inaccurate
Have a look at the last post (27) on the sticky http://www.rcuniverse.com/forum/m_86...mpage_2/tm.htm
Make sure you use a ngk or rcexel cm6 plug, the dle one is useless
Let us know how you go.