I assume you are talking about the new 2011 Skyhawk kits gasbike/Kings are selling? The ones with the old CNS ver 1 carb
with all the plastic tubes, POS air filter that is too long so they include this long lame Z intake pipe opposed to Ver 2 CNS that had an idle mix screw, red flat filer, and only one vent and drain tube?
I got 2 in last week 2 in earlier this week and 2 more on the way from gasbike.
The first orders were different, no telling what the new ones will have.
*Buying Tip... on the Buy page of gasbike you will find 2009 Flying Horse kits are discontinued but let you get a 2011 for $5 more, $10 less than that kits buy page.
Anyway, if your seat tube angles back enough that old CNS carb/filter will fit with a regular intake, I put one on my bike to try it out and it runs great.
I have a new kit/used bike build with GT5 Z-intake old CNS I suspect you have and it runs pretty well, if you can call running as fast as a stock 2009 48cc with NT carb fast, but it has the same issues you have, wildly fluctuating idle.
I'll try to get back here with findings but I am have a major issue with the fiber optics going to my server so other than a temp page I have set up, my KC's Kruiser site is down all but this http://vales.com/KCsBikes