I experienced something similar. On only three occasions a few weeks apart I got caught in mid summer stop-and-go (mostly stop-and-stop) traffic in Houston. It was inch forward and wait over and over. The temp gauge was at the top, but on the gen2 the radiator never overheated to the point of spitting coolant.
When the traffic cleared so that I could actually accelerate, the engine wouldn't take more that a little throttle without bogging. After each tenth of a mile it would take a little more throttle until after half a mile it was running fine.
Since this happened only those three times under identical circumstances, I assumed the fuel in the float bowl right next to the Very HOT exhaust pipe got so hot that it bubbled on the way through the jets which restricted its flow and that as I rode slowly on the air passing by the bowl and cooler gas from the tank lowered the temperature in the bowl allowing the engine to run properly.
I wrapped some exhaust pipe insulation around the pipe next to the float bowl and never had the problem again, but I also stayed out of rush hour traffic, so who knows.