Won't idle in cold weather until warm.
 

I have 2001 2500 5.9 gas. If the weather is colder than 40 degrees it will flash the check engine light and die until the temp gauge rises above 130. If I keep my foot on the accelerator at about 1500 rpms it will just dog down and recover rather than die. It also doesn't show any codes even if I have a computer hooked to it when it happens. I have replaced the idle air control (IAC). I ran some sea foam through it, which didn't help. Any thoughts?

Check fuel pressure. Monitor engine temp via your scanner while warming up, see if engine temp is actually where you think it should be.

See what various sensors have to say when the engine is cold, compare that to what they think when the engine is warm. (MAP, TPS, IAT)

Could easily be an intake gasket leak, when it warms up the aluminum expands enough to seal the leak.