Need help with cold idle settings

[TubeTruck]

So as the temps have been dropping here in Chicagoland my truck is finding it hard to stay running. On a decent day I come out in the morning, step on the gas pedal once, fire it up and it stays running. High idle is usually around 1k rpm, by ear (I don't have a tach, that will happen when it warms up a bit). Lately though that hasn't been the case. As the temps have been hovering around 0 it's been hard keeping the truck running unless I keep my foot on the gas. It starts ok, then you can hear the rpms drop slowly until it sounds like a thumper cam, then stalls. Now I have to crank and feather the gas to get it to start which kicks down the high idle. It had a tune up this past summer so I don't think that's much of an issue but I do know the engine needs a rebuild. It's got a Holley 650cfm spreadbore on it with an electric choke, performer intake with the heat crossover active and a 1/4" thick gasket under the carb. I'm thinking about raising the idle setscrew so it idles higher but that just seems like a bandaid to me. Should I raise the idle higher? What else can I do to help it?

 

[Craig 85]

I can't recall if you are running a stock air cleaner or not. I am on my truck and ran into a similar problem this winter with my truck after I made some adjustments this past summer. I noticed that the flapper on my air cleaner snorkel was not opening even when warmed up. I pulled and plugged the hose so the flap stayed open. This stopped the chugging when the truck was warming up. It also helped with the re-start if it died during warm up.

It's been 35 years since I ran the Holley Spread bore on a car. Can you adjust the choke housing like a Quadrajet so it delays the pull of?