3.0 P0172 and P0175 codes

[caposto]

I bought my 2002 X5 3.0 a year and a half ago. I was getting these two codes every now and then but now its more regular and I've got a smog coming up. They are "Bank 1 too rich" and "Bank 2 too rich." The only thing I could find was it could be a dirty AFM so I cleaned it and the contacts but no change. There also seems to be no rhyme or reason to when the codes are tripped (hot, cold, accelerating, idling, etc.) P0172 trips first and then shortly after I get P0175.

The service is up to date on it so was hoping you all could point me to possible causes. Any help would be much appreciated. Thanks!