P0107 & P0452 Codes MAP sensor

I keep getting these codes P0107 and P0452 one is for a MAP sesnor and the other is low voltage something or other. THe dealership cannot figure out the problem. Has anyone else had these codes and had it fixed. What is it????

What year is this, low map/baro input refers to the map/baro sensor having low input to the pcm, the sensor/wiring/vacuum circuit are all possibilities here. The other code is a problem with the evap press. sensor inputs, again this must be checked visibly and with a bi diectional scanner checking the sensor inputs. Some GM pressure sensors have been bad but this must be diagnosed.

1999