FWIW, if there was 100 octane or q16 at the pump across the street for $4/gal, and if my 555cc injectors would keep up with the power, I would run one of those instead .... but there isn't. I put very few miles on the Z ( maybe 1000 in the last 6 months), and when I do I want to be able to enjoy it without worrying about blowing it up, at the track and on the street. The car is one toy among many and will never see any long trips except for to the track which there are several of within 200 miles ....
I suppose that there is a way to get 500rwhp on 91 pump, but that is way too laggy and expensive for me ;-)