Idle drop by 500 rpm?

No. you can take the PV out and throw it in the ditch and it will not affect idle. POWER valve. It's on the POWER circuit. Not the idle circuit.

I tried to point out that it sounded like a vacuum leak and advised you to inspect for such many posts ago. I'm backin out of this, because now you're going in so many directions, I'm not sure you'll ever get it right.
Well, I'm just spitballing RustyRatRod, it started Blasting Rain and lightning, plus it was dinner time. So I was simply asking if that would do that. My Bad, Dude. All my Lil Non Rubber caps are there. Cause the Rubber ones dry rot In a year or so. The carb base and intake were wiped w/ a Lil Alcohol yesterday, plus it sounded and ran killer, at first. When it backfired through the carb, could it have split a cap? Other than pulling the 3/8 line to the brake master, I'm not sure where to look... any suggestions? Could the backfire have blown the intake gasket? If I knew, I wouldn't be bothering Ya! The only actions I've taken a Wrench to, is ones You kindly gave me. My Bro Doug has a 770 on his 460, he said he'd bring it by at one point. The ol lady, him , and I will be outside, cutting bad stucco, replacing a door jamb, painting, and doing a metal roof over a mobile home this week, so I doubt I'll get to do but a Lil at a time... sucks Bro. If You care to give me a list, to work down, Id Greatly appreciate It Rob! Close the secondaries first? Then Do the timing w/ a vacuum gauge? I'd like to rule out a vacuum leak... hell, I don't know where the heck to start, i just wanna get there! Thank You Rob!