MAF

I suspect when you changed the MAF you somehow failed to reconnect the vacumm port or broke the fitting. On many 3800 engines, there is a black plastic vacumm fitting with 4 connections....sort of looks like a big "H" one of the lines goes to the heater control to use vacumm to open and close the heater vents. Another clue...usually the cruise control will not work because it is not getting vacumm.