I ran into this problem on one of my conversions, a Stihl 62cc. That conversion demanded a custom intake be fabricated, and while the one I created had an insulated portion, it did allow heat to be transferred to the carb via the carb mounting bolts. This caused nasty tuning, running, and consistency issues until I remedied the situation.
In your case, I wonder if the cooling effect of the alcohol in E-85 fuel would help out if you switched to that fuel? Also, I don't remember if you had to lower the compression to successfully run gasoline in your case, but if so a switch to E-85 would allow you to raise the compression ratio back up and gain some power back.
AV8TOR