2001 Ford Windstar cuting out, misfire on cly 3

Engine Performance problem
2001 Ford Windstar 6 cyl Front Wheel Drive Automatic 140k miles

I was working on my sable, and came acros a product called sea foam. So I used it on my sable. I liked the results so much I used it on my windstar, and have been having problems ever sense. I have changed the idle air control valve, because it deterated the diafram in the valve. Cleaned the egr valve, and changed the spark plugs, they were the sugestion of the parts house. After 140k they tend to open the gap, and it did 3/16''. So now most of my problems are solved, but it still cuts out when you are barly pushing on the gas pedle, not all the time just every once in a while. I just put a plug in the vacuum line on the egr to see if that's the culprit.
Will the egr leak and cause this problem, or would it be all the time.