Ford 7.3L Power Stroke (1999-2003) :: F350 DRW - Chugging Bucking At Highway Speed

I have recently picked up an older F350 2WD 7.3 DRW Lariat. the price was right higher miles but hey it is a 7.3, overall in very good shape.

So the issue at hand is the truck runs great most of the time and puttering around at city speeds you would never know there is any issue;

Get the truck out on the highway set the cruse at 70 to 72 and if you hit a rise in the road or other reason to slightly accelerate the truck chugs and bucks. For lack of a better description it goes chug chug chug, if you accelerate harder to downshift it goes away or if you back off the throttle it goes away. This happens with cruse on or off, a steady foot on the pedal will cause this as well.

I have also noticed that when you let off the throttle the sound the truck makes de-fueling is just very different and "off" sounding . Not sure how to describe it but it sounds funky ... clearly not right when compared to other 7.3 or my 6.0 truck.

What I have done, :

1. Had the truck scanned with an AE and a snap-on scanner both show no codes ran injector tests no contribution errors, not even in # 8.
2. Changed fuel filter
3. Changed Oil and Filters ( tried both full synthetic Rotella and Dino oil looking for a difference )
4. Cleaned out the fuel filter housing just in case.
5. Confirmed injector O-Rings are not leaking

This feels like a fuel issue, my next thought was start looking at fuel pressure under load at speed to see if there was a drop when this is happening ?

Is there a way to test fuel pumps in this truck ? Maybe a clogged pick-up screen ? Where do I start looking next ? I have reasonable mechanical skills but don't know this motor very well, this doesn't seem like a CPS issue..