I'd say fuel starvation for sure. First thing I'd suspect is the accelerator pump, then float level. The carbs rebuilt within the last five years are going to have components that are compatible with today's fuels. Outside of that, components will deteriorate. It boils down to what the carb was rebuilt with, since there's NOS kits out there. The smog carbs did run leaner, but that shouldn't have the effect that you're experiencing.

Case in point, I bought a NOS reman 1bbl carb a year after I bought my cammer. After installing it, the car ran great! But six months later, I started to get a whiff of raw gas. I didn't see anything until it started staining the intake. So I had to buy another reman carb that was put together with current fuel acceptable parts.