CAT C15 /6NZ trouble continues

Thanks to EmodelCATman as well as spsauerland for that info.
Today wasnt too bad with the stuttering etc. I came to a traffic light and, like usual, obsessed and thinking constantly about this problem, i was flicking up/down my high/low selector on the shifter. Twice i did that and "CHECK ENGINE" LIGHT CAME ON. But thereafter, engine ran better than the previous 2 hours since leaving the house. Also, "ABS" light kept coming on/off with brake application. A short while after i dropped that trailer and hooked to another (both trailers the same 5 axle end dumps of the same year, 2013) and the same "ABS" light illuminated on/off with brake application, so i know it wasnt the first trailer with an issue.
On another note, i had a call from a very inteligent sounding fella , "Greg" , i believe a independant mobile tech with 20+ years CAT experience (thanks for the contact, to another fella on this forum trying to help me, without his permission im not going to mention his name, but i am very grateful) Greg lives within a couple hours of me and after we spoke, he is going to meet up with me on Monday ( Jan 08 2018) on my truck lane, to ride along with me , loaded trailer, and as he says, "i think i know what your problem is". A dedicated to the job sounding guy, with CAT experience.
18th gear still sluggish, very much so. Soon as i get it in the slot (18) it seems like theres zero power on the pedal. I can hold the pedal down 1/2 way or push it to the floor, no difference. Im constantly keeping my engine speed at/near 1500 rpm so to create enough power to pull the load. 1300 can also be sluggish, with no response, no extra torque, no pulling power anywhere on the pedal above 1/2 way down. Engine basically holds that torque with nothing more to be had once at around half throttle / 50% or so.
I also had a call from another fella in Indiana, also a technician and also a great guy with dedication in his field. He offered a couple injectors or ECM if needed.
I must say, theres still alot of great "salt of the earth" people out there, old school guys who have a bucket load of "i give a sh**t" in their person. Glad to have found this site. Thanks again to the so many who continue to help me.
And to the fella "Brandt" (posting above) who mentioned Pittsburg Power, yes, i spoke to them about 10 weeks ago, but unfortunately im in Canada and dont run the States anymore ( i put in 26 years running produce and floral out of the Niagara (Ont.) penninsula, muti drop down the eastern seaboard from Boston to south Carolina. In a way, i miss it, but i missed so much at home during those years, and am fortunate to have a great family. Only to earn enough money to pay my daughters prescriptions ( she is disabled) did i run the 6 day/weeks state-side, it was all for the family.
Anyway, i look forward to getting together with Greg on Monday, and will mention the info herein posted by both "EmodelCATman" as well as "Spsauerland" and another fella with info for my dilemna.
Thanks again guys, i really appreciate it all, and welcome any/all other info y'all and/or others may have.
Till tomorrow.
And should anyone feel they (or i ) can benefit from calling me directly, or texting me, my number is ; 905 746 5505 and my name is Dan.
Thanks again.

 

Thanks for your support. No welding was done at all, as i confirmed visually myself and thought of when it all started , which was the first day, the first load i pulled, about 18 months ago now. What a journey its been. But thanks to guys like you with still some caring and wish and want to help, i think im getting close to the end of the problem.
As im typing this, i was thinking. Although the previous owner said "NO" when i asked if he ran a Bully Dog or any other such tuning device, theres 2 velcro spots overhead of the drivers seat, one with power wires to it. The stereo already has/came with, satelite radio. The spot where his GPS was mounted is very clear, and on the ECM is a (approx) 12 gage wire coming out of it, about 8" long, with a female type butt connector on it. CAT guessed, saying "its probably a power supply of some sort" as they held the hood about to close it one day. But now im wondering if he (the prior owner) tapped into it with a engine power booster of sorts, like a "Bully Dog" or similar, and now the ECM is (the best i can say) "confused" ?
Well, i will put it before Greg this coming Monday, along with the other info so many guys have been helping me with.
Thanks again

 

I had a fuel sample sent to both CAT as well as the chevron lab. Both confirmed no combustion was in fuel. I had a retired tech stop in, pull all injectors and install new O rings. That was around 14 months or so ago. All O rings/seals were perfect that he took out.
Great thought though.
Thanks again

 

I also considered the fact that my split fuel tank (right side) was bleeding hydraulic oil onto the other side (the fuel side) but it wasnt. Thats exactly why i asked the weld specialty shop in Toronto to put 2 walls in the tank, with a 1" air gap/void, between with a hole drilled at the bottom of the air gap so if the wall leeked it would be easy to identify with a leek from the hole, but they said theres too much pressure on the wall from 80+ gallons of hydraulic oil and nothing on the other side (like fuel pushing back) so i asked, what then if my fuel is low in that tank on the other side ? They said its a time thing, if there would be nothing to push back all the time everyday it may cause an issue over time. But with fuel there, even half full, the pressure balances out during the time. Long and short of it all, they said they wouldnt do it do to past issues. The tank was pressure tested for 24 hours after building it. Originally, i bought a slim line 80 gallon hydraulic oil tank, cat walk mount, but the nose swing of the trailer went into that space(when we measured) so it was ruled out, and had to go with 2nd choice, split tank.