Q: I got a 04 ford ranger 4x4 with the 4.0sohc and this has been giving me a headache. She runs fine when cold but when she warms up

I got a 04 ford ranger 4x4 with the 4.0sohc with 125,000 miles and this has been giving me a headache. She runs fine when cold but when she when she warms up it starts run rough. It idles at 550rpm with a flutter. I've done a lot of things to try and fix it even took it too 3 mechanics and the did no justice. I did a new plugs and wires,cleaned the iac valve,new pcv valve,new coil pack,all new vacuum lines,new battery,new knock sensor,checked the egr she's good, new dpfe sensor,new camsensor, all new gaskets(even valve covers), checked all grounds they were good,new fuel filter, new air filter,cleaned the map sensor,checked throttlebody sensor it's good,cleaned throttlebody with seafoam. I just don't get it. she also has a ping that sounds like it's coming from the egr tube but there's no leaks it's still shiny. Just want to know what's going on with this motor and why she won't run right

My car has 125000 miles.
My car has an automatic transmission.