2004 XC90 Turbo R&I issues 2.9L

[Jtward401]

Id like to preface this with sayin i am NOT a Volvo tech, have avoided any kind of Euro work thruout my career...i have A6 ASE in electrical, and mainly solve body electronic problems, and C level tech work. but i started a new job, and the tech im replacing left this nightmare with me.
The car was smoking and losing oil initially...owner had it for a month...Volvo dealer told him Turbo 2 was shot (cylinders 4-6, bank 1)...it was replaced, but after disconnecting down pipes, bank 2 cyl 1-3 was full of oil. This was where i came in, and im only tech at shop, and owner doesnt mind if i take too long and dont know what im doing.

Realized the intake was full of oil...exhaust pipe had a lot of oil coming out while running...installed two used turbos (turbine blades were shot on original turbos, and wastegate didnt work with vacuum applied, the junkyard turbos passed these inspections). I got it all back together and realized on turbo 2, previous tech reused exhaust manifold gasket...reinstalled...now had massive coolant leak.

I learned of the thermostat housing breather/bleeder issue...if you try to remove or even wiggle the timing cover, this bleeder nipple breaks off because its plastic (stuff like this is why i avoid euro cars), so got a new metal nipple (MUST USE THREAD SEALER) And hose fitting (the hose fitting is also prone to failure), and after 4-5 days i had this poor car back together with no exhaust or coolant leaks.

Its got 128k on it...i understand that the turbo failures probably led to damage to the catalyst, the PCV system, the intake, and most likely fouled the spark plugs pretty good...got a PO306 type A dtc...flashing MIL and rough misfiring above 2000rpm...actually tried to pull plug to look at it while awaiting the thermo housing nipple to arrive...felt pretty tight, didnt wanna even chance breaking it because i want this thing gone and i dont know if this guy can afford anything else to be done on it. The air filter is full of oil...engine doesnt seem to be losing oil or any other fluid...and damage to turbo control valve, MAF, O2 B2S1 and probably the downstream as well.

The car is still smoking pretty good after 30min of idling and light driving...stil) flashing MIL...readiness monitors arent all set yet.

My theory is spark plugs are fouled, causing misfire, and that the turbo oil seal failures that brought the car here in first place caused catastrophic damage to pretty much every engine subsystem, and that this thing SHOULD be smoking and misfiring right now.

The customer just wanted it drivable, and not sending oil into intake/exhaust, he understands it will run bad...im just wandering if dirty exhaust should go away (and when), and if im missing anything here, or if maybe this car was misdiagnosed from the get

Told guy he needed new spark plugs and air filter, havent sold it yet, but i dont know how hard i should stress the idea. And wondering if turbo control vlave or oil strainer should get replaced