First off, thanks in advance for any assistance.

Owner of a 2003 7.3 Excursion. Bought it a couple of months ago with 123k on the odo. Have about 1k/1.5k under my own belt with it. Lately it has a vibration/shudder at highway speeds. Specifically the top end of 3rd but only very slightly, most noticeable in 4th/OD at lower RPM's (1200 or so). Feels like a misfire to me but there is no discernable "surge." Truck starts fine warm or cold, no smoke, idles nicely. Problems/lack of power existed before the expected switch to winter mix fuel.

I've pulled the valve covers and replaced:
- UVCH on both sides. I had honestly hoped to find burned pins but instead I found clean harnesses with the ford TSB clips already installed. I had already ordered new, revised, UVCH's from International so I opted to install those and kept the old UVCH's with clips as spares. Gasket connectors were good so I re-used them.
- Injector O-Rings
- Glow plugs (preventive - since I was in there and didn't know the age of the existing ones).

I checked the wire harness going over the driver side valve cover and found the bottom wires to be chaffed. I electrical taped the problem wires and added a short piece of heater core hose as a loom/preventative measure.

Replaced the rear driveshaft u-joints.

Checked and the front ESOF hubs are properly disengaged (tied fishing line around the axle shaft yokes and inner-C and drove around - fishing line was still in tact afterwards so I know the shafts are not turning).

Problem is that I still have the shudder at speed and what I feel to be a lack of power.

HPOP and IPR duty cycle are where they should be and the EBP/V is operating as it should.

Took the truck to a reputable/quality transmission shop and they said the torque converter and transmission was operating as it should be ("no problem here Jack").

Ran a buzz test and all injectors buzzed evenly but I got P1293 and P1294 (High Side Open).

CCT failed injector #8 but I have the recall Gray CPS so I read that this is expected.

Ohmed the valve cover gasket connectors and all plugs and injectors ohm out as they should (GPs = 1.5 ohms or so, injectors ~5 ohms to the center pin).

I've not ohmed the harness between the IDM and the valve-cover plug block.

Am I looking at a new IDM? From what I've read the IDM usually causes a no start issue and more codes when it goes bad and I am hesitant to replace it without being more secure in the decision that it's the problem. Any advice would be greatly appreciated!!