I have a little experience with Sunoco that I would like to share with everyone. One night we were running the dyno late into the night. The fuel we were running was Ammoco 93(the clear stuff). Well we ran out and had one of the new guys run out for some. the Ammoco station wasn't open so he got the next best thing, Sunnoco 94. Now Sunnoco runs 10% alcohol in all of their grades. When we started running the motor with the Sunnoco,we lost 3-5 hp on average. We reset timing, retuned the fuel maps and after optimizing everything we were still down 3hp from the previous runs. The temperature or barametric pressure didn't change much in the lab going from one fuel to another although the dyno converts to SAE Corrected hp and torqe anyway.
Anyway, take that experience as you wish. As for me, I stay away from Sunoco from now on. Just figured I would share with everyone.