before I moved to europe I ran a 4:1 mix of 91/E85 for a good 2 years
that bumped up the octane enough to run 20psi on DSM 13g's and DSM SMIC's without knock, my fuel mods were 580cc injectors and a hotwired walbro
I also dynoed 343hp/356tq at 18psi, the car had
WAY more left in it, long story short (24 bent valves
) I didn't have time to get it tuned very well before going to the dyno so I stayed fairly conservative