Basicly, The spark plugs were shot.
I had been running BP7ES's, on account of the motor being forced fed. This coupled with the tune being very rich, and a couple of severe floodings when I ugraded the fuel pump, meant that they could no longer cut it. I tried everything I could think of, but it wouldn't go right. Then a mate of mine who crusty holden V8 which was doing the same thing, came right with new plugs.
Problem fixed.
goes to show, even almost brand new plugs can let you down. I'd had no problems with them when I was giving it death. But too much inactivity created the problem.