Today I had sudden onset rough running in my 115 hour 912ULS powered Kitfox Vixen (with Ivo three blade ground adjustable Ultralight prop). Mag checks were okay, temps all around seemed okay however there was a decidedly very rough mode. I made a precautionary landing at the nearest airport (after considering I may have to come down wherever necessary). Propeller looked okay, I took off top cowl to look for signs of what it may be. Could find nothing out of the ordinary. In the meantime a RV 6 pilot showed up & parked next to me. Turns out he also had a Kitfox Model 4 back home with an 80 hp Rotax 912, so he was very interested and helpful. The reason for his stopping at this airport was to have supper with an old friend (arriving in a car). His friend showed up and the three of us looked & discussed ideas (plugs, CDI failure, bad ground, contaminated fuel, carbs suddenly out of synch, fractured carb boots?). My new RV/Kitfox friends friend noticed that one of the three stainless steel leading edge tapes was missing. We were guessing this may have caused an out of balance situation, I peeled off the other two leading edge tapes and did another runup. Things were much better vibration-wise, so I did a lap around the pattern and flew home with things running just fine. Now, to clean up the blades and put some tape back on. My RV friend had been more than willing to fly me home (about an hour’s trip). What a guy.