So I replaced my faulty MAF sensor about a week ago (week ago, week ago) and today I got hit with a P0172 which is running rich/lean. Could that have anything to do with the new sensor picking up something the old sensor didn't? Or just coincidence that the bank 1 and or 2 went?

 

Did you replace you MAS with a Delco? Aftermarket MAS don't meet the ridged specs GM put in for these cars.
The new MAS could be causing that code but it could also be that now that you have gotten the new mass the before cat O2 sensor is bad and not reading right.

 

Yes it is an AC delco. Read a lot of threads saying that you def have to have AC delco parts for our cars to work properly. It could just be a bad sensor. Good thing I'm getting a zzp down pipe soon

 

A bad MAF could cause the code, but so could a bad injector(s) or Bank 1 O2 sensor. Since the MAF was the last thing worked on prior to the code I would go back to it and double check your work. Maybe a leak around the mounting flange?

 

Where exactly is this Bank 1 sensor 1? And is there a bank one sensor 2? Print out just said bank 1, not specific to which sensor.

 

It's located in the rear exhaust manifold.

 

Which sensor is the best to use on our cars? Bosch?

 

I would use an AC Delco or a Delphi - BUT - I would double check installation of the MAF before spending any more money. You may end up buying something you don't need.