I get why we only have 91 octane here. I'm pretty sure boosted cars don't care about altitude. Wouldn't my car see KR above 4* using 91 octane?

My thinking was that with a 4.0-4.2" pulley I could eliminate KR on 91 octane fuel, and still have similar power output to a 3.8 pulley, 91 octane and more KR.