SEVERAL POSSIBILITIES, HOWEVER before you go to far, check the underside of the AAM to TB corrigated inlet hose. Very common to chaff on the underside and allow unmetered air. Also consider possibility of chaffed or cracked vacuum lines that may seal themselves when engine warms up. If you have not cleaned the Throttle body, it may be a good idea to check it. Don't discount the idea of cracked injector seals that expand and seal when warm.

I have found this problem tends to originate from the air side of the equation rather than the fuel side. Let us know what you find.