1997 Ford F150 4.6L v8

Problem: got the P0401 code began to fix the issue resulting in the truck now starting with a high rev around 2,000 rpm then slowly coming back down to around 800, sometimes jumping back up then stalling out completly while in park. Hesitation and mild shaking. Also the sound like clicking not sure where that is coming from most threads said exhaust manifold leak, but I don't see any cracks and replaced gaskets.

what I done so far:
took apart intake manifold and cleaned ports
replaced egr valve
replaced egr tube (that connected to exhaust manifold)
replaced idle air control
replaced dpfe sensor and tubes
replaced mass air flow sensor
Replaced exhaust manifold gaskets

any help to figure out why the truck starts at a high rev then slowly stalls in park. Could it be PCV valve?

 

Pull the throttle body and see if both of the two EGR ports are plugged.

 

Check the rubber PCV tube elbow behind the intake.

 

thanks already did that ports are clean and free

 

Symptom commonly seen with a vacuum leak.

 

You can easily search for vacuum leaks using an UNLIT propane torch.