Yeah agree I think the e-mix likely provides a cooler combustion burn so knock is lessened as are EGTs particularly on a long pull doing 60-130 or a standing half mile where the stock exhaust and intercoolers have a hard time keeping up.

I haven't tried pure 91 since getting tuned and I haven't driven a stock .2 yet so I will def take your word that the stock .2 is faster on 91. Which is pretty amazing.