the high hole in the carb brings gas to the "choke" (enrichener) circuit, as well as the idle circuit which ends as a small hole next to the diffuser.
Make sure you can get cleaner to pass all the way through the idle circuit. if it does not go it is probably clogged at the point where it passes around the outside of the diffuser. It is a little strange, and you do not really need to understand it if it is not clogged, but if it is, you must take the diffuser out.
If you need to remove the diffuser, make sure to use a screw driver that fits the diffuser holder perfectly. if you try with a screwdriver that is not a perfect fit, you will strip it out (like Anthony Did, and I have done) and you will NEVER be able to remove it.