I have also experienced what I would asume is some kind of break-up/surge with my car on
e85, tt happened as the turbo was spooling up to peak boost ~3500-4000, under high load and typically happened more often in 4th gear and higher. However, when I turned my boost up past 28psi it went away, dont know why. Maybe if you turn up the boost and it goes away, you can figure out more about what is ...