Idle drop by 500 rpm?

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!
It's ok. It's not you. I'm trying to give you a diagnostic map and you're gettin railroaded around every corner. I realize now I just caint do it from here.