NOOB E63 owner, need help!
 

I am throwing a few codes, that sometimes go away, and sometimes show back up, usually after some spirited driving. I do most of the work myself, unless it's major maintenance, maybe someone has run into this. the codes are the following, P2187, and P0171, and I have already replaced both MAS sensors, any ideas? O2 sensors maybe? any help would be much appreciated. thanks in advance.........

could be intake manifold leak or o2 sensor...