I've had my 2010 5.7 turbocharged for over a year, over 11k miles and hundreds of passes. 93 octane, no meth. Have also done e85 when it's convenient but most track days were on 93. Don't get hung up on the boost number, that doesn't necessarily tell you how how hard it's going to be on parts or how much power it's going to make. Mine makes almost 600 wheel on only 7 psi and runs high 10s @ 126 in a 4000 lb stick shifted Jeep.