I don't think it's air leaking in the shaft. It is not uncommon for oil to leak from the shaft so that tells you if oil can get out then air can get in. That's normal and doesn't harm a thing (except make a mess if it drips on your carpet). If it won't idle that can be a symptom of being too lean on the bottom end. It can also be a symptom of being too rich. It will set there idling and load up on fuel and flood itself out. I still say you have a problem in the low end needle valve. You may try a plug with an idle bar if all else fails.
OPjose is right about the spring clip that holds the high end needle valve being too loose. I've seen that a few times on Evolutions. I cut a piece of fuel tubing and using needle nose pliers slip it over the needle valve and clip. That holds pretty well.
I've seen a bunch of the Evo's of all sizes and only seen a couple that didn't perform just fine and that was usually due to a bad plug or a hole in a fuel line or something else real simple.
WCB