It may in fact be a torque convertor issue, but it does it in a gears. I guess you could say it feels like a miss. I'll hook a vacuum gauge up this after noon to see what I pull and how steady it is. Supposed to be right around 20 I think.
Graham, I had suspected that also. I know when you touch it your fingers turn black. It's beginning to get on the rotten side. I'll pull that cap off and stick my finger over it to see if it changes.