Is the spring I showed in my photo actually part of the break booster vacuum valve, that scattered when the valve failed/exploded?

Thanks very much for the information. I thought it was vacuum or or pcv, but I never would have guessed brakes.

Is it unusual that I haven’t noticed any degradation in braking, cold engine or otherwise? The thing was (is) clearly in pieces and not functional.

Meant to say that the spring was sitting loose on some "hoses," not on holes.

I recently had a ton of work done to keep my 2004 XC70 alive, including a new fuel pump and replacement of the failed turbo with a salvaged one. Car runs ok, but yesterday when I checked the oil, I noticed a 3" long steel spring sitting loose on holes and a two-piece black plastic part cleanly ...