Austintx2004

Hello guys, I have a 2004 S600 that I need some help with. I noticed while plugged into icarsoft that my B28/7 pressure sensor slightly fluctuates, and is reading significantly lower than the other 3 pressure sensors. With the car off, all four pressure sensors read about 1000mbar, but when the car is turned on, B28/7 lowers down to about 300mbar. Is this normal? The car is down on power, and feels like it is not boosting correctly. Other than feeling sluggish, the car runs great, and does not misfire at all. Any suggestions would be greatly appreciated. Thanks.