Power valves are designed to optimize low end performance up to about the 4,000 rpm range. Since most hillshooter & drag bikes are launched at a high rpm anyways, the power valve would be ineffective right from the start. Especially when you shift at 7,500 + rpm. Your rpm drop might be down into the 5,000 rpm range if you are short shifting.

Mr Hall would be better to provide the specifics.