What are the ambient temps? Just an idea but your carb could be getting cold or slightly icing up on your way to work, I had this issue with my car. The O2 sensor made it a bit easier to figure out, carb would go super lean and stumble. Once I got off the highway and sat in a bit of traffic it would warm up and be fine.
Big reason why I went with a non-Air-Gap manifold this time
