Morning Tim, alot of variables go into it, bottom line is to use the thinnest oil/std vol & psi pump that will maintain a safe PSI for your eng/app. Idle can actually b low if it jumps up right when you goose it and on the high end for a dragger 8-10 psi per 1000 rpm is a safe ballpark figure. I'd b way more concerned w doing the proper internal mods rather than what the gauge shows at it's highest point when it exits the filter & goes up to the sending unit