How much oil in intercooler is too much oil? No rev above 2000 RPM

[chemist_slime]

Just installed a brand new intercooler from ATM after putting off an oil leak for almost a year. Car has roughly 103k miles and was leaking about 1 qt of oil every 2000 miles which I later identified as coming from the charge pipe on the turbo side leading into the intercooler. (Dealer said it was a return oil line leak and wanted 6k to take turbos off to verify. I politely declined.)

During that time, the car still drove fine unless I was going up a steep hill (15 gradient) where it would occasionally give an "engine malfunction, loss of power" etc but it still drove without issue. Weird?

Fast forward to the past few weeks. After replacing the intercooler, car is now in limp mode but there is no visible oil leak. However, once I start the engine, I cannot rev beyond 2000 RPM. After clearing all codes, restarting engine and holding down the pedal, after about 5 seconds, I get the dreaded CEL.

BlueDriver showed:

P0299 Turbo Charger/Supercharger "A" Underboost Condition
P204F Reductant System Performance Bank 1
4530 Status: History - charging pressure control, control deviation
46F2 Status: History - DeNOx-System, function

I just replaced mass air filter, all the vacuum lines, except the ones going under the manifold and down to beneath the turbo. I also pressure tested the 2 vacuum solenoids following A. Rods youtube videos and Sunny who's a member of the forum. (Big thank you!)

I decided to take off the intercooler again to inspect within and found quite some oil but do not have enough knowledge to know if it's too much or normal. Car has not been driven at all and merely just been turned on/off a handful of times. The original intercooler that was removed did not have this much oil inside, but there was a leak at the hose so it's hard to compare.

Any clues?

[BigHunk]

Probably your turbo is bad, to be precise oil seal inside turbo.