I was definitely in the camp that said if you have fuel problems, there must be something wrong with your car because it doesn't happen to me. Until... going up Mt. Mitchell off of the Blue Ridge Parkway. I also had similar problems in Mississippi after hours of sustained 50mph driving. At one point I noticed rolling bubbles in the sediment bulb. It was hard to take a good picture of that, but I did get a picture of the giant bubble that formed as the moving bubbles stopped. I had a couple days with similar conditions and with multiple fill-ups per day I know it wasn't just one particular tank of gas. Higher octane gas didn't seem to help. It pains me to say it, but after adding MMO the problem went away over the next couple of days and 1000+ miles.
More information on the trip here:
http://www.sheepisland.com/3000modela/
