Just an FYI, I took my carb apart because I was suspecting a float level problem, and I found that there was no needle hanger! the needle was just resting in the seat! I think this is what caused my underload bog at high rpm. I haven't been anle to do exstensive tests yet but I think I fixed it.

 

Not sure that was the actual cause of your problems (I've had more than a few q-jets and variants, have found the same condition upon disassembly with no actual fuel starvation problems prior to disassembly), but you may have fixed it anyway. The fuel pump should be able to unseat an unloaded needle valve - if not, a plugged fuel filter or weak fuel pump may be the actual cause.

To be sure, it takes less fuel pressure if the needle is being raised off the seat by the float weight.