Detroit 14L... Mystery problem, no one seen before.

Been hesitant to post this because it's a lot of info for such a small problem, nobody I've talked with about it seems to have a answer, but here goes.. 2006 Columbia, 14L with 10 spd. 780K miles, not been rebuilt as far as I know, I bought it used. I've driven the truck for 50k miles and only in the last 10k miles have I noticed the problem. The best way I can describe it is on any sporadic occasion the engine will feel as though someone is turning the key on and off very quickly or maybe your hitting the acc. pedal up and down very quickly.. During this time the boost gauge will go from 40 to 0 to 10 etc. just bounce around! You can let off and ease back down on it and sometimes it will go again with no problems or it may continue doing this for 10 miles... It may not do it again for a month or two.. It is VERY SPORADIC. I actually got lucky and had a freightliner service manager with his computer hooked to the truck and it actually starting acting up! However, I do not know everything on the computer that it is monitoring, but he did say that the TPS was showing full throttle as it was acting up. So that's ruled out.. Every parameter being monitored was in check as far as I know. No codes showing either! When doing this acting up, everything still works as normal and all the gauges are reading normal. He said in 18 years of being a freightliner tech, he has NEVER SEEN A TRUCK ACT LIKE THIS BEFORE... I have spent a lot of money on brand new parts because I fully intended on keeping the truck for a long time. I have replaced ECM to firewall harness, ECM to engine harness, injector harness, fuel pump, fuel pressure valve on back of head, ignition switch, batteries, "light bar" (computer) on dash etc etc etc... I DO KNOW this is NOT a problem with a vpod, turbo, or any related component, so don't even let that be a thought.
Here are some problems I have found and fixed. I did remove and clean all ground connections I could find attached to the frame, I think 6 in all.. 3 positive wires with fuses that go into the battery box were corroded very bad in the fuse holder, I cut the wires down about 6-8 inches and replaced with new fuse holders and connectors. (Maybe the rest of the wire is corroded where I can't see it??) The battery cables under the protective sheaths were very corroded and I cleaned out under the sheaths best I could and also made sure there was a clean connection on the new batteries. (I have new battery cables coming tomorrow just in case they are a problem). Also the truck would leak water in behind the driver door and down on the fuse box and abs brake box, as most trucks I've read have this problem... I replaced the fuse box with a new one but I DID NOT replace the wabco brake box... Could this have something to do with the engine cutting out???
My only other ideas are ECM power/ground wires.. battery cables that run from the battery box to the front... Injectors (I've heard they usually start to give problems around 700k miles)... A ground behind the dash or in the cab that I haven't looked for yet. Or finally the ECM itself... I intended on replacing all these items and if it still doesn't work, I give!!!
Give me some of your ideas as I am almost ready to throw in the towel!! Thanks in advance!

 

When I bought the truck, I cut the tanks so I could clean them with a pressure washer on the inside as they were black. 50K miles letter they are still clean and debris free.

 

The reason I say it's definitely not the turbo is because I have tried a different turbo, thinking exactly what you are and the result was the same. I was able to make a video on one occasion when it was acting up because someone was with me when it happened. I wish I could post the video on here but it was made with a cell phone and I'm not sure you can post videos anyway