I think a more accurate question would be at what RPM do your secondaries open on your 4 barrel and the gas consumption goes way up. I am curious as well. My 454 in my Baha loves the gas, but I usually just burn it and get to my destination. I think it's somewhere around 3200-3400 rpm, but not sure. I know it's more vaccuum related, but there has to be a typical RPM range.