I have always had bad experience using lower grade gasoline in performance engines. My dad borrowed my car once and he filled it up for me when he was done. He put regular gas in it. The difference was immediately noticeable. Mileage and performance were down. After a quarter of a tank I syphoned the rest of teh gas out and we put it in my dad's Dodge Ram. Seems to work OK there, and he has a big v-8 in it. Filled my car back up with high-test and everything was back to normal.
I also think it will keep your engine better over time.