My brothers 2001 S400 got sluggish all of a sudden and when we checked the error code it read as P2025. After some googling, we though that the fault was in the part that I linked and we bought a new part. But when we changed it today, it gave an error and the car was running "slowly". When we remove the part, the car runs as if there was no problem though so we don't know what is causing the problem.

The part: Part - Album on Imgur

Ps. Sorry for my sub-par English, I tried my best.