brake booster
the one that is in there is aftermarket. looks like a older style black ball they used as a float in the tank of a toilet. i showed it to a guy who's worked on my car before and he said it was a specific one. i only let him change my oil but he knows alot about cars and some about turbo's. not really wanting just anyone to change it if it's something specific. called autozone and they don't carry it, and orielly's has it for under 300 but i didn't see it as they had it in stock and there wasn't a pic of it on their CPU.