582 Slight EGT Rise/Roughness

During a one hour flight last evening in smooth/hot and humid conditions, over a period of time at relatively even cruise settings, I -think- I noticed a slight (50-75 deg F) EGT rise on both cylinders, and -maybe- a slight increase in vibration. It was very subtle, and came on over the course of many minutes. I feel like this thing is whispering to me that it has a problem coming on, but I'm not quite understanding what it's saying. Does anyone have any troubleshooting suggestions?  Customer airplane (Kitfox II) 582 "gray head" supposedly upgraded to "blue head" by Lockwood. All my experience is with air-cooleds, so I am a little bit out of my comfort zone.