Thanks for all of the responses so far.
As an update, I pulled the exhaust off the manifold, no change except a lot louder! While had it off I checked the heat riser. Naturally it was frozen, I got it freed up and in the open position, again no change, so as great an idea as it was, we can rule out an exhaust blockage.
I will follow Harvesters methodology and see if that helps root this out. I replaced the plugs, no change, replaced the condensor, no change, I have checked the insulation around the bolt that passes through the side of the dist, found it in good shape. The wiring harness is all brand new.
Thanks again Guys, the input is very appreciated!
Tim