Audi 80 1.9 tdi pump (?)

Hello dear community! I have been the proud owner of an Audi 80 1.9 tdi BJ 1993 for a few days now. I don’t know so well about the 1.9-er tdi engine, but I have really good experience with the predecessor, the 1.6-er td(i). And now to my questions: 1. I’m surprised that any pump runs after the engine is switched off in the engine compartment (is connected to the valve for the turbo limitation). Is this a normal function? What’s the purpose of this? My battery was taught yesterday, had this follow-up under suspicion… 2. The engine itself doesn’t feel particularly strong, but does not develop smoke when giving gas. It runs through (some mast), but at a speed (about 2000 rpm) starts to whistle loudly at the turbo. Does that say anything about the condition of the loader, or should I look for a leak in the cover? MfG, Attila