First start hesitation

[supermanRc51]

I have a 2000 expedition with a 4.6 , when you first start it it acts like its running out of gas under acceleration then it goes away and runs great till you let it cool off and then go again. I have replaced the fuel pump, fuel filter,plugs and coils, intake gaskets , alternator , not all for the same reasons but this is the last issue and I'm running out of ideas

 

[JUST4FUN]

fuel pressure regulater on the fuel rail , has a vaccume line going too it