Jacks1821

So I got a 2006 gmc 2500hd with the 6.0 vortec. The truck idles really really rough. Like it almost dies when it’s up to temp and in park or at a stop and It makes a loping sound. The weird thing is, it drives fine once you give it some gas. I’ve replaced the throttle body itself, replaced the TPS, replaced the mass airflow sensor, I’ve even changed the air filter itself. I’ve checked the spark plugs but those are fine. I’ll also note that I replaced the intake manifold gaskets because those were pretty bad. I’m really not sure what else it could be because like I’ve said, once you give it some gas and start to go it runs perfect but as soon as you come to a stop it almost dies. Any help is appreciated.