Overheating Issue

Lets fine tune where your talking. Raw water on the metal can or rubber hose?
That water should be way below engine coolant temp.

Sent a PM.

That may or may not mean anything.
Scenario 1; Suddenly issue develops.
Scenario 2; All debris in system gets packed down after many hours.

The UN-cooled exhaust between the head and water cooled manifold log?
Under power, you can cook on these short passages. My sep-son heated up leftovers here before I replaced our dead inverter.

Resized for Boomer

I'm going to call this a 6-71 TI, not a 6-71 TIB.

I also see it's vert tight back there remembering it's the stb main.

Also MES from 2002?

Under the heat shield (blanket wrap), keeping the riser tight to the turbo is a large V clamp.
Pick up a new clamp.
Remove this clamp, the water hose and loosed the 5" exhaust hose.
The riser will fall away from the turbo. With a twisting motion, the riser should come out of the 5" hose.
Big Screwdriver opening up the hose a lil bit and squirting wd40 in that opening between the can and hose should help.
Raise the riser up. Have a Nerf football or small boat fender (anything 5" & round) ready to stuff in the hose should sea water want to splash in.

Wear old gloves during this. The inside of the riser at the turbo may be covered in black slobber, the metal edges could be sharp.
And there is wire in those hoses.

Did you ever get a temp reading (under load) rite where the decal or MES stamp are located?
Or even the 5" hose itself?

Yes.
Take a bunch of pictures from all angles. Looks like the bottom right will be blind to you where some hoses go down..
Evenly snug bolts up, no need to kill them.
Old school is WP grease on the gaskets and seals, lock-tite on the threads.

Well, your not extracting the last 75 to 100 hp from the same block.
You have to remember, the 6-71 started life as a 2 valve 100hp rocket in the 30/40s.
Very dependable and bomb proof. Go-zillions of hours.
Throw a 4 valve head on top, turbo, inter-cooler and big A injectors for big HP numbers, something has to give; engine life.
What HP tune do you have? Covington, J&T, DDC, S-S.
I like the plain white and dry turbo, I think DDC, 385hp?

Yep, Your rite, 485hp from TI.
F.M.