Hi Guys, I finally got some time to look at this. The brake fluid is clean and not filthy plus the level is good indicating it was flushed in the recent past.

Unfortunately it appears that there is definitely some "foreign contaminants" inside the brake booster - video below. Also, there is some sludge build-up inside the vacuum hose as well - photo below. This must've been caused by a failed check valve.

Here is a look inside the brake booster with my snake cam: https://streamable.com/qunk0



To rectify this, I plan to change the following parts:
- Brake Booster
- The vac line from the vac pump @ front of engine -> booster

Questions:
- What is the best "pressure bleeder" to buy?
- Do I have to replace the master cylinder? It adds quite the cost to the project.
- I'm tight on funds right now, is it worth grabbing a booster from a wrecked X5 (after verifying that it is oil free of course) and just replacing the vac line or am I asking for trouble doing that?