P2108: Well….. considering the other problems, I have to believe this might be a result of the rest of the stuff that’s going on. It’s like if someone tells you’re bad at playing jenga, but they kick the table everytime you’re about to pull one of the blocks. I wouldn’t focus on this for now.
P2281 is for a vacuum leak between MAF and throttle body. In this case, it means, turbo intake pipe, turbo, intercooler piping, intercooler and throttle body hose from intercooler.
I believe that even with a busted turbo, the engine should idle fine. but it will lack a lot of power when you drive it or add load and will trigger the CEL for sure. Also, you mentioned a stiff brake pedal. I think these two symptoms are related, meaning there is a lack of vacuum at the intake manifold. I would check the PCV check valve a the turbo just in case:
Here it is:
Also, while in there, might as well pull the PCV system to refresh it, I did a writeup a few months ago here:
If I were in your situation, first of all, I would do the compression test, check the cylinders with a borescope to see their condition. If it’s all good, then just replace the turbo, pull and clean all of the intake parts. And I mean from MAF sensor to cylinder head. Why? because of you don’t want more debris going through the engine, and because you’ll get to inspect thoroughly. The lower intake manifold has a gasket that works with the PCV system, it has reed valves that reroute the PCV gasses depending if there is boost or vacuum at the intake manifold. If they’re jammed, you’ll have a vacuum leak and rough idle. That turbo check valve I posted above? same deal, it works with the PCV system and will affect idle if jammed.
Turbos, you can pick one up from a junkyard, any S40, V50, C70 or even 2012-2015 S60 with the 2.5L T5 engine uses the same turbo. Be careful when removing the exhaust manifold nuts, soak them with PB blaster for a couple days and use a wire brush to clean the threads of the stud before attempting to loosen them. And go slowly (NO POWER TOOLS!) if it starts binding tighten it back, clean the thread and try again. When installing the new turbo, use new lock nuts and make sure to reuse the thick exhaust manifold washers. The convex side goes away from the engine, these play a key role to not break exhaust studs.