[wiswind]

At the top of the forum page is a sticky post about a TSB (Technical Service Bulletin) that talks about a problem with 1999 and newer windstars with the isolator bolts having the "isolator" break down from exposure to oil.
This causes a problem with vaccum leaks....and can cause problems.
The TSB also talks about the DPFE.

The EGR valve is pretty reliable on the windstar.

The IAC is a mini accellerator.......controlled by the PCM.
This is how the PCM maintains the idle speed under varying loads when your foot is not on the accellerator.
This can stick.....and cause stalling issues when turning the steering wheel during parking manuvers....and such.
So...I do not think that this is your problem.

Another thing to look at is the IMRC ( Intake Manifold Runner Control).
This will be on the passenger end of the lower intake manifold.
There will be a acctuator that connects to 2 shafts......1 shaft in each bank of the lower intake manifold.
On this shaft are plates or "butterflies"....that open and close a 2nd port for each cylinder.
On the newer windstars (1999 and newer) these are electrically driven.....and the problem that comes up is that the nylon clips that connect the shafts to the actuator break....fall off...or otherwise become disconnected.
Sometimes one side is connected and the other side is not....which will cause a imballance condition between the front and rear banks of 3 cylinders.
Unfortunately all my pictures are of my '96....which has the older vaccum actuated version.....

For a fuel system cleaner....I have tried MANY and the one that works best for me is Berryman's B-12 Chemtool in the metal can.