Is the computer really this sensitive?
 

I've been loving my mini ever since I purchased it. I've never had a problem with it until installing a "cold air" intake, honestly for the K&N filter. This very quickly threw a P2096 (Post-catalytic fuel trim too lean bank 1) and dealt with it for a couple months, condemning O2 sensors and MAP sensors, only to finally give in and put back the old filter. I noticed the diameter of the stock tube is slightly smaller and fits flush with the lip of the throttle body. I just couldn't believe the ECU refused to do something about the air intake. Is this a common thing? Did I really need to bring it in to remap it for a little K&N?

Ok, whoops
 

Was definitely looking at the wrong thing. After a quick fuel pressure test, loads under boost seemed to drop, everything else was normal.I assumed since the pressure during prime and startup were normal, but open loop wasn't, the fuel pump should have been healthy. After a quick fuel filter change, it's like a whole new car and no more P2096 code. I've had this code since I bought the thing, instantly installing the intake without test driving it first honestly.

Definitely wasted my money bringing it to a shop to be told "it's your K&N".

I don't know if this post would be helpful to anyone with this code in the future but if you have definitely ruled out air leaks, replace the "lifetime" fuel filter and see if that changes anything.