Although that is what Holley has said for many years, a lot of tuners feel that it is outdated and do not use it. It us often too late of an opening point, especially if the idle/cruise is a bit lean. I personally like a clean idle and cruise if I can get it and that means that I usually end up with a 9.5PV. There is not much wrong with a PV opening early, but certainly a late opening can be very noticeable.

The rating opening point varies a little bit. Some PVs begin to open at the rating while others are well on their way. And things are usually happening very fast at that point, so exactness in not usually necessary.