Engine Code Help

[BMFBUFF]

Had my timing chain done and it runs great @177,000 miles. However got some codes a week ago and cleared them to see if they would reoccur which they did about a week later. Codes are:

Ambient Pressure Sensor
Secondary Air System (Cyl 1-4)

Anyway to isolate what would bring these up in tandem?

Thanks in advance

[psjr]

I haven't seen anyone actually fix the pressure sensor since it's built into the DME. Here is some info: http://e38.org/m62tu.pdf - page 21.
(http://e38.org/m62tu.pdf)