Slant 6- Idle and Running

Have you checked to see that the hot air valve in the exhaust manifold is operating correctly? I also agree with what @pishta said. If you don't have inspection in your area, I would 86 every bit of that smog era stuff. There's absolutely no reason for it now other than to pass inspection. not saying any of that is the problem, but you'll never know with it all on there. Say for example, the EGR valve is not all the way seated closed because of carbon buildup. That's a manifold vacuum leak right there and one I've seen more than once before. I'd have a block off plate there in a Georgia minute. But again, non e of that may be the issue. It could be though. That's the disadvantage of online diagnosis. lol