2006 4300 Durastar codes FMI8, FMI6 and FMI5, could use a little help

Good day all, and I want to say thanks to you folks reading this. So with all the help I received here I was able to isolate and repair the turbocharger issue that was preventing me from going over 45 MPH. Turned out to be a plugged catalyzing muffler(who puts a catalytic converter INSIDE a muffler?!!). But many of the codes I was getting before are still present and the issue(s) seems to point toward bad ECM or faulty wiring. But I wanted to ask you all for any advice you may have to offer.

So I'm down to three codes...FMI 8, FMI 6 and FMI 5.

The SID254 FMI 8 code seems to be intermittent power or ground to the ECM, or a problem internally with the ECM. I would think if that were the case there would be some symptoms with the way the truck is running, but we just drove it 500 miles round trip and it ran just fine. So I'm a bit confused. I cant find any bad connections or fuses at the battery or at the ECM, so I might just replace the ECM power relay and see if the code re-populates.

The SID27 FMI 6 code seems to be a bit more complicated. The pulse width modulated signal sent by the ECM seems to set by a plethora of sensor signals...EBP, Altitude sensor, engine speed, accelerator position, barometric pressure, EGR position, and a bunch of other data. But again, the truck seems to be driving fine so yea.

The SID1 - SID6(getting all 6) FMI 5 code relates to the fuel injectors. I'm thinking the Ignition Driver Module might be having some issues...possibly low battery power. But again, the truck drives like a champ!

During the trip back from Oregon the check engine light came on for a couple minutes, but then turned off, which is why I checked for codes.

If anyone has any advice on any of these error codes it would be most welcome.

Thanks!

-Monte