Changed new lower intake gasket and upper intake gasket also new valve cover gaskets

New pcv valve, new air filter, new sparkplugs new wires,

No check engine codes or anything,
The van doesnt start right up u have to press on the gas all the way down and turn the key to crank it up, after leaving it a few mins on the van will start right up and the next day u have to do the same,

It stays on as long as u want when its parked,
But when i want to drive it and put it on gear it drives but it looses RPM's untill it reaches 0 and shutts off , but starts right up,
I checked the fuel pressure and its good ,

Any ideas?

 

I think you might have a bad or leaky injector. When you floor it the injectors are shut off sort of like starting and old carburated motor.

 

Any codes or Service engine light?
Might check the fuel pressure while it's running; rev it up from the throttle cable and watch the fuel pressure. Is this still a return style fuel system? If so, the pressure regulator is in the fuel filter.