84 Chevy K10 idling high

So I have this problem I can't figure out. Got a 1984 K10 with a 305, Quadrajet, auto, 4x4. It's rusty and a project but it runs fantastic and the 4 wheel drive works awesome. Just recently though it started acting up. When it warms up the idle runs really high, almost like the choke is fully open but it's not I checked to make sure it wasn't sticking. I tried blipping the throttle like when you set the choke, nothing. I put full length headers and dual exhaust on so it has none of the original emissions junk on it, but that was before the winter and it has run fine all winter. I also rebuilt the carb around the same time. The only recent thing was a month or so ago I replaced the starter. Then today after work I was tinkering with it before I went inside and I manually opened the vaccuum secondaries, tada the idle went down to normal. But as soon as I released the secondaries it ran back up to really high. This is starting to get irritating and when it's slick out it makes driving a little hairy. This weekend I'm going to try basic maintenance stuff, plugs, seafoam, and some other stuff. Any input from the more learned guys on here would be awesome. Thanks ya'll.