I have the Dinan, and live in CA so I can only run 91 as well. My thoughts on the Dinan is that the tune is pretty conservative, but all of their stuff is. Im not bashing Mark D's tune, being a tuner myself, I just wanted to slap something on that I knew would be on the conservative side. Lets face it, there isnt a whole bunch of power to be found in our motors, but having the higher rev limiter was #1 for me.