I have picked the power valve like this for the last 30 years, hasn't let me down yet. The power valve is really just the off idle to full throttle transition. Its all in how your car drives.
And that's the way Holley does it, BLP does it and countless other and it's still not the best way to do it. Doing it that way opens the PV so late in most cases that you get a tip in stumble and guys try to cover it with accelerator pump shot.
Why all these people are telling people to tune like that is beyond me, other than its easier to check vacuum at idle rather than get a longer hose and run it into the cab.
In the small block forum there is a video made by Mark Whitner who PROVES a power valve doesn't open at idle or affect idle. So what your idle vacuum is is rather irrelevant when it comes to setting PV opening.
