Jeff
My understanding is that the blended fuels can cause issues with the inside of carbs getting gunked up or dirty. Some have also mentioned that there might be an increase of possible issues with "vapor lock" with blended fuels. Here is a couple of the previous threads that discusses the subject.
Carbs Damaged By Blended Fuels by Wbulk
This is new: stumbling/missing at idle/cruise speed by Dangerous Doug with help from Patrickt