What would you check next?

[boostin20v]

My '07 runs extremely rough, but haven't found the exact source of yet. Issues started when I hit limp in 4th at around 115mph full throttle, that's been happing for a while but diagnosing something like that has been hard. This time when I hit limp I didn't have my BT obdII setup on my new phone so unable to clear while driving quickly and attempted to limp to the next exit. Now with the CEL on and RPM limited trying to limp the ~.5 mile it was like I hit the smoke screen button, thick cloud of white smoke any time I was on the throttle and as I got to the exit the cluster oil pressure warning message displayed. I stopped quick and a oil check showed no oil. I got towed to my buddy's shop where I later checked the oil and added about 4.5 liters to get proper level on the dip stick. Grabbed codes/cleared them and started car. Runs like there is a massive vacuum leak.

I've basically just dumped the car at the shop, nice to have friends in the business as he did some testing but not sure where to go from here. A smoke test was done, but test doesn't show much (a bit of a leak from the MAP as my 4bar doesn't fit the CTS FMIC piping that well) but nothing else obvious. Car has been burning more oil recently, added 3 liters in the last 5k, but hadn't otherwise been running off. The oil burning has mostly been averaging 1.5 liters per 5k for the last few years. Plugs look wet as you'd expect, turbo cold side not an abnormal amount of oil, hot side dry. Borescope after the plugs pulled shows expected carbon on some valves but nothing damaged. A leak down was done on two cylinders (didn't say which), pressure didn't seem bad but he said he could hear/feel air out of the dip stick and when running that it was shooting smoke out of the dip stick.

So as I'd expect with my oil consumption and milage (275k) I have a ring issue. Could that alone cause the crankcase pressurization being seen? Where would you go to dig into it further?

Pulled codes:
5 Faults Found:

004243 - Bank 1; Fuel Measuring System 2
P1093 - 008 - Malfunction - Intermittent
Freeze Frame:
Fault Status: 00101000
Fault Priority: 0
Fault Frequency: 2
Reset counter: 255
Mileage: 441780 km
Time Indication: 0

Freeze Frame:
RPM: 2940 /min
Load: 5.1 %
Speed: 85.0 km/h
Temperature: 86.0 C
Temperature: 36.0 C
Absolute Pres.: 990.0 mbar
Voltage: 14.097 V

000564 - Boost Pressure Regulation
P0234 - 001 - Limit Exceeded (Overboost Condition)
Freeze Frame:
Fault Status: 01100001
Fault Priority: 0
Fault Frequency: 1
Reset counter: 255
Mileage: 442543 km
Time Indication: 0

Freeze Frame:
RPM: 4122 /min
Load: 98.0 %
Speed: 187.0 km/h
Temperature: 87.0 C
Temperature: 45.0 C
Absolute Pres.: 980.0 mbar
Voltage: 13.589 V

000257 - Mass Air Flow Sensor (G70)
P0101 - 004 - Implausible Signal - Intermittent
Freeze Frame:
Fault Status: 00100100
Fault Priority: 0
Fault Frequency: 1
Reset counter: 255
Mileage: 442641 km
Time Indication: 0

Freeze Frame:
RPM: 4125 /min
Load: 33.3 %
Speed: 187.0 km/h
Temperature: 85.0 C
Temperature: 39.0 C
Absolute Pres.: 980.0 mbar
Voltage: 14.097 V

000566 - Manifold Pressure / Boost Sensor (G31)
P0236 - 004 - Implausible Signal - Intermittent
Freeze Frame:
Fault Status: 00100100
Fault Priority: 0
Fault Frequency: 1
Reset counter: 255
Mileage: 442643 km
Time Indication: 0

Freeze Frame:
RPM: 3704 /min
Load: 19.6 %
Speed: 80.0 km/h
Temperature: 84.0 C
Temperature: 36.0 C
Absolute Pres.: 990.0 mbar
Voltage: 14.097 V

000022 - Bank 1: CMP Sensor (G40) / Engine Speed Sensor (G28)
P0016 - 008 - Incorrect Correlation - MIL ON
Freeze Frame:
Fault Status: 11101000
Fault Priority: 0
Fault Frequency: 2
Reset counter: 255
Mileage: 442646 km
Time Indication: 0

Freeze Frame:
RPM: 2041 /min
Load: 8.2 %
Speed: 58.0 km/h
Temperature: 87.0 C
Temperature: 36.0 C
Absolute Pres.: 990.0 mbar
Voltage: 14.097 V

[boostin20v]

No suggestions? a bit surprised

[Older_not_Wiser]

Overboost code at 98% load and 187km/hr. MAF code shortly after could be caused by excessive blow by. Almost total loss of oil unfortunately probably points to ring issue as you surmise. I suppose it could be a head gasket or cracked head as well but I would expect oil in the water or water in the oil as well.
Tough luck, keep us informed

Not exactly sure what should be checked next. Compression maybe. Pressurize cooling system to check for cracks. Ring issues are hard to confirm, leakdown being the best but not always definitive as it can be valves, etc. a well.