Ignore the ecu codes on that car, they are worthless information. At that
point they didn't have the fault checked together at all.

First thing I'd look at is the AIV valve and make sure it isn't dumping
exhaust gas through the MAS/AF meter whatever you want to call it. Sounds
like this may have happened and ruined the MAS.

Another thing I've seen on high milage cars is the engine is using some oil
and giving a bad signal to the O2 sensor. It see's the oil as fuel and
leans out the engine. Try running it with the O2 sensor unplugged and see
how it reacts.

Same with the coolant temp sensor, there is a subharness connector on the
pass side of the plenum and the computer does into a default countdown
timer setting for the temp when it's unplugged and run. if that helps
replace the sensor AND the subharness. It's a mother to get to and requires
a funky special tool to remove without taking the front of the engine
apart.

Hope this helps you get in the right direction.