if you get the car here we'll come fix it but it might take a week of us visiting your cap cod house. I got dibs on the sofa.

I'm worried about the quality and filtering of your fuel. crap/water is clogging up the injectors. Just detach the pressure lead at the rail and put a hose on it and turn the key to position 2 and pump it all out. replace the filter. (again)

low speed overheating is related to the auxiliary fan not operating.

It sounds like one of the cams a tooth off, have you rechecked timing? if thats good then the turbo control dump valve coincidence may hold some sort of clue. additionally, the ox sensors may have been damaged by over heat and water vapor. its nearly 100% that the problem is related to the event or ...

these cars are only affordable if you do your own work. but dont scrap it, sell it which is a way of passing it on. how ever if the state will give you 1500 then thats hard to pass up. (or replicate by selling)

you say you started it. You either have it right or close to right or the valves are bent. did you turn it over one rotation by hand and check for interference and recheck the timing marks? (plugs out to make this easier)

Its rarely the injector. You could swap it to another cylinder and see if the code changes to that. Volvo uses a inexact batch fire that
sort of equalizes out in the plenum to produce 14% fuel to air. check the routing and pinching and age of the HT wires including the coil.
if you are dead set on ...

I guess its the rack. slight possibility the strut bearing on the top that lets the strut turn with the steering is bad, but I have never seen that.

did you swap the trans computer?

all the turbos are the same. return line off the pressure damper. why are you getting new ones?