If I may make a suggestion here-
Since your kart's not yet built, and your engine is absolutely brand new, I would advise you to leave it alone for now, and get the kart built. Once the kart's done, run the engine bone stock until the warranty expires. If you modify it, and accidentally damage the engine, you may have warranty issues if they figure out you messed with it...
Besides- Until you build and test it, you really won't know what you need! Except for the muffler that I built, and a minor governor tweak, my GX340's all stock, and any more speed on that thang would be frightening! In fact, I'm thinking of gearing down a little more...
