2002 express van vapor locking?

We can drive this van for a long time between this problem. Than go to start it and it will idle rough it you don't keep your foot on the gas. (these have a been long distances) Then this began happening more frequently. Just had the cap, rotor, plugs, wires, air filter, distributor. Friday, went short distances and the same problem occurred. A friend of our said it's trying to vapor lock. Could this happen or what else can be going on? again this is a 2002 express van.

No on Vapor locking.
But I would check the fuel pressure when it does it.
Also secondary ign and EGR valve.
How is the tune up?
Ever been tuned up?
Post back fuel pressure reading when it is acting up.
Any check engine lights?

This thing has never given a code for this problem. Besides what I listed what is included in a tune up? I will have the EGR checked.

Fuel filter and fuel pressure.
How is the fuel pressure?
Good AC-dELCO PLUGS?