After I remapped the timing, the bog was nearly eliminated. In my situation, the symptoms you describe were timing related. The cold start-up sequence calls for 35' BTDC at water temps below 135'. After about 110' F., I can see the timing begin to back off until it reaches the normal operating temp timing of 15' on idle status. I know that you don't want to start messing with your timing maps, but I'm just saying that I had a similar occurrence when I was re-mapping my timing.