General Slant and Gas/Octane ???

What are the octane ratings listed on the pump you are using? What is the alcohol content? The alcohol content can have a very large effect on idle quality. I used to see a negative reaction when going from 87 to 89 in my old volare. The 89 had 10% alcohol and it wouldn't idle as smooth as with the 87 straight non alcohol gasoline. I did a google search on racetrac gas stations and couldn't find their supplier. I suspect alcohol differences, but I could be wrong.