on going 2000 S80 T6 problems/issues
 

With all the following, can anyone give me an idea as to how much further in this “Volvo S80 T6” tunnel of darkness I might expect to go before I see some light?! What other super common issues might I expect to have? Please share anything I have not listed…..promise I won’t cry.
Repairs made to my Volvo 2000 S80 T6 with 129000 miles
Rear brake pads
Broken fuel pump plastic housing
Squeaky glove box latch
Clunky sunroof glass
Drive axles right and left
Control arms w/bushings
Sway bar links
Turbo boost solenoid
New transmission
Headlight lens right side
Most vacuum hoses due to rot

Maintenance done as follows:
Spark plugs changed
Fuel filter replaced
Transmission filter and fluid twice before replacing transmission

Accessories done as follows:
Custom sheepskin seat covers
Wood grain look dash kit
Leather (wrapped) steering wheel cover
Current issue to address is no oil pressure message, plan of attack is to drop oil pan and replace o-rings and clean tubes, screen, etc.

What we found once we dropped the oil pan. A very bad o-ring on the tube to the oil filter housing.

Does it leak from the oil filter housing or just creates a lack of oil pressure in the the filter?

it just caused no oil pressure. which triggered the message "no oil pressure stop engine" and after researching that warning through forums we concluded that it might be the oil pump or o-rings. Glad it was the latter.