How nice would high octane gas be?

Building an engine that requires higher octane than what's available from the pump is totally unnecessary nowadays. WIth the great flowing heads that are available along with good intakes, and other smart parts choices make a high octane street motor kinda stupid, really. Save it for the race track. Even then, there are a LOT of pump gas race motors out there. Using race gas where it's not needed can even cost power.