Ok, I think I have finally found the problem, maybe. It seems the knock sensor has become too sensitive. It thinks there is a knock. When this happen the ECU starts knocking timing out of the ignition. Each time it sees or thinks it sees a knock it knock another 4 degrees of timing out and also richens the fuel mixture. It had gotten to the point where the timing was about 20 degrees less than required for good performance.
The result was an over rich mixture and almost no advance of the timing under a load which made it run very poorly and really suck gas.
I am in the process of fixing it now and will post the results.
Paw Paw