CAT C15 /6NZ trouble continues

Question Troy.
How did CAT figure out the injector seats were not cut right ?
I'm trying to get CAT over here to consider this, even though I just found out that when CAT pulled the head a few weeks ago, and sent it to machine shop, the seats were in fact NOT cut even though they said yes they were.
Liers..!!!

 

Ok guys, it's over...finally.
Wanted to be 200% sure before I said that.
Here's what it was and how I found it.
As followers of this thread know, for 2+ years I did it all, CAT did also, 99% CAT did was warranty under my Platinum warranty plan.
After CAT and everyone else poked at the bear, I always continued on my own, changing every sensor, every wiring harness, fuel pump, fuel supply line, you name it, even pulled the tranny, as it was always in upper gear pulls that the engine? stumbled shook and lost power as a result.
One day a month ago , staring out the windshield, I started to think I messed up on a stratoflex fitting when building a fuel supply line, thinking I forgot to live the hose before threading on the tapered section and I cut a flap inside the hose. So , easy enough, I re connected the old supply line.
No change.
One day, a few weeks later looking at that capped off new supply line, I thought just maybe I'll try connecting that newly built fuel line to the return side. So, because the return line is normally a size smaller, I bought $110 in adapter fittings. I crawled under the truck, connected the new stratoflex fuel return line, and Monday came around.
I fired up my 6NZ and in 5 minutes I knew I had fixed it.
No stumble
No shaking
No power drop off.
I pulled out the old return line 6 days later, cut it open, inch by inch, until I found it.
Years of hot fuel returning had degraded the rubber, a flap hung down inside the hose half way between the engine and diverter valve.
The way I figure, the fuel temp sensor , before the head , told the ECM, my fuel temp inbound was ??? Let's say 100 degrees. But nope, the return line flap restriction had that fuel much hotter, maybe near boiling.
The ECM wss regulating fuel injection via the temperature sensor, but it was wrong info, thanks to the fuel return line restriction.
Smooooth. Unbelievable smooth running.
Can't thank y'all enough.
Its been a trip guys, and a expensive one at that..
Great thanks to Swaan, engine machinist, and the so many others who stood by my side, ready, willing and dedicated.
Hope I can return the favor one day.
I'll be around, looking, hoping to help another owner op or just anyone in need.
God bless, my friends.
Again, great thanks.
( and, thinking about what one of y'all said many pages back..
☆☆ and that's the last episode, the final season, you were all waiting for on this Netflix series that seemed to go on forever ..

 

O. And " BIGGUNS", I know you said " if it were a flap of rubber, it would have blown past by now"
All I can say is,...anything is obviously very possible...
Great thanks to everyone. !!!