Background:
09 Clubman S
98,000 miles
Mostly original parts (no mods or upgrades)

Car seems to have good power most of the time, but every once in a while, and only seems to be going uphill, it feels like the turbo doesn't kick in, and the car goes into limp mode. Then by the end of the trip, or the next day, the car is running fine again. The limp mode light stays on for a bit, then turns off eventually. Then, about a week later, going up a hill, it happens again.

The first time this happened, limp mode lasted longer, and I took to a mechanic. They "fixed it", then I got limp mode that same day. They "fixed it" again.

Here are the things that they have replaced:
Valve Cover (with OEM)
Ignition Coil (aftermarket)
Brand new turbo (with OEM)

I'm tired of throwing money at this mechanic, especially if they can't really fix the issue.

Here are the codes they gave me from the last time it went into limp mode. I made them write them down instead of doing any more work. Well, this is what is scribbled onto the paper, if it makes sense to anyone:

2A56
2885
2A75H/10879
F7SC
9314

The hills are in the Catskills, typical East Coast mountain range driving, if that is necessary info.

Any ideas? Where to start?

Oh, I should mention, before all of this went down, the thermostat housing was replaced with OEM. It cracked open and leaked coolant all over. No, I did not drive it like that. Had it towed.