99 S80 2.9, what is happening?
 

I picked up this car a couple months ago for $2200. It's in brilliant physical condition, mileage is high at 184k. Since I've had it I've put about 1k miles on it.

When I bought it, the CEL was on. I trusted the guy that it was o2 sensor, and I forgot my obd scanner, so whatever. Got it home, and it's Bank 2 Sensor 2 throwing a fault, as well as "gross egr leak", according to the scanner. That would explain the ~25mpg.

Since then, the car has been being very weird. It's sluggish, which was something I was led to believe wasn't an issue with these cars. Once it's up to speed, it'll hold it fine at ~2500rpm. I did oil and plugs right off, old plugs read fine and oil wasn't bad either. Car has a very nice service history, belts look perfect, all seems well. Not sure if bad O2 would cause sluggishness.

EDIT---Removed a bunch of weird behavior because now it appears all connected to the ABS module, save for possibly a transmission error that came and went quickly. I came here to ask about a harness failure but nevermind I guess. I do fine electronics repair and would like to attempt the fix myself, but I can't seem to find a tutorial. Any hint in that direction would be appreciated!