I must say, I'm at a point now where I don't really do anything to my distributor while it's in the truck. I love my SUN machine, and I'd rather go to the hassle of removing and re-stabbing the distributor so I can get it tested and set-up with confidence on the distributor machine.
Once you've eliminated the distributor function as a culprit, you can look into other areas, though I scratch my head as to what they could be. Had a fire truck that fell on its face on the highway. Turned out the fuel pump wasn't keeping up. We connected a pressure guage to the fuel lines and drove it, the pressure was dropping over 35 mph.
I suppose a carburetor float that was set to high would be staying closed too long before letting more fuel in.
If it isn't timing advance, and it isn't lack of fuel, I can't figure what would cause it to bog down only in 3rd gear.
-Michael
