Not building heat

After getting home today I let it idle In the garage and it came up some in temp. I have it at 12* initial and 34* total before vacuum advance, whatever that is with the MSD distributor. On really cold days I think the choke is staying closed some.(I disconnected the cold air tube to the aircleaner as well) Edelbrock 1406 carb. Its getting worse than normal fuel mileage also. It gets warm in the truck but it takes a little bit and not hot like it has in the past.
I'll look at changing the metering rod springs to lighter ones and see if that helps any.
Thanks!