That is one of the problems with getting numbers anywhere close to accurate from Desktop Dyno. That version should have an option to input port flow numbers at various valve lifts. There are probably flowbench test results posted on the internet. Try Googling it and see what you come up with. Remember though, even with flow numbers you need to take Desktop Dyno results with a grain of salt. But.....it's better than a kick in the pants I suppose.