Rough Idle on deceleration

[Mustangflyer]

Hey guys I'm new here (and to powerstrokes, well diesels in general) but I am very mechanically inclined. I just purchashed a 1997 7.3 F350 4x4 and I noticed a slight problem Im having.
On deceleration the engine seems to be stumbling, missing. I originally noticed it while getting off the freeway. Once I stop and give it a little throttle it maintains a good idle.
Ive been reading and trying to self diagnose this and since have changed the oil, oil filter, fuel filter and cleaned the fuel bowl and regulator screen.
More messing around in the drive way I noticed that if I let off the pedal quickly it gets the rough idle, whereas if I let off slowly it will return to a normal idle.
I checked the pulse width at work with my scanner and it shows when its stumbling it drops to .3-.6, but back at idle returns to somewhere around 1.4
Im thinking TPS maybe, but I keep reading about the EBP sensor...if the back pressure was too high would this cause it to starve the engine of fuel?
Any help is greatly appreciated, Im at a loss now. Thanks guys!

[Mustangflyer]

Okay, so I finally got a hold of the guy I bought it from and he said that it has done this ever since they put the exhaust on and removed the cat. He said, that whoever did the exhaust told him it would have a rough idle because there is no back pressure. Does this sound right?