454 tbi won't idle when warmed up...

[Nodnarb76]

So I have been working at this for a while.
Problem is when truck is first started (cold) it runs fine, then when warmed up, and I let my foot off the gas pedal it dies. It will restart if I give it some gas ( press gas pedal just to be clear) while starting but then dies when I let off the pedal.

When this started I was getting a code 44 lean exhaust so I replaced o2 sensor, fuel pressure regulator, fuel pump, and fuel filter, even a new gas tank and cap.
And the problem remains.

Prior to this I have replaced: erg valve, map sensor, coolant temp sensor, and cap,rotor,wires,plugs.

Any ideas/suggestions?