The Ford Festiva stalling issue came back when the gas tank hit the 1/4 level point. Something the chainsaw repair guy said after he tuned up our Stihl recently got me to thinking. His comment was that he had to use his special carburetor bath 4 separate times to get all the gunk cleaned out. This prompted me to give the Festiva another Seafoam treatment, and it took over half the tank before the problem finally went away, but it's running like it should now and it's all thanks to Seafoam.