03 T&C with 3.8l engine, 160K miles. still runs like a champ!

My cruise works correctly15% of the time. On my way to work I set the cruise at 60 mph. most of the time just after I push set the speed slowly increases. if I let it go I may be doing 75 mph. then it will eventually get down around 60 and mostly stay between 55 and 65 mph.
It worked perfectly until I changed my radiator. Now this. I know! I know! That had nothing to do with it, but that is the last repair i made before the CRAZY cruise started.

ANY SUGGESTIONS???