Well, I think I'm making some headway with this.
When the carb arrived from the rebuilders, it came here to Canada from the USA. I guess Customs wanted to make sure there was nothing nefarious in the box so they poked a big ol' hole in it. Like say, with a screw driver or something of that size. Anyway, when I had opened up the box I noticed that the hole was punched straight through to the top of the carb and the vent hole was plugged solid with cardboard. A hole in one right? A perfect straight shot right to the vent hole.
I was pretty pissed at this and I actually popped the top off the carb to blow out the cardboard. I didn't go any further than this.....I saw all the dry cardboard sitting on top of the gasket so I used some compressed air to get rid of what I saw and put it all back together. When I installed the carb, it ran great so I figured I got it all. I guess not.
Look at all the boogers of cardboard I found in the float bowl. There's bits of it everywhere too that don't show up well on the camera, all over the top of the float and stuff. This is a real downer, but par for the course for me and my luck these days. Pretty sure this is causing my problems?