Are you running a wideband O2 sensor or did you just have a tune done? If you changed the O2 sensor for a wideband, did you change both banks 1 & 2 or just one of the O2 sensors? I'm still going to say that the O2 sensor might be bad. Your code said bank 1 (PO172). If that sensor is malfunctioning then it will throw the EGR code too as it relies on the reading from the bank 1 O2 sensor.
If you're running too lean then your engine is making combustion too fast and hot and would trigger your EGR code.
I've had map and maf sensors go bad on me without throwing any code before. However, you are getting an O2 sensor code. Just because you've been through 3 doesn't mean anything. I've replaced O2 sensors that failed within 6 months before. The sensor going into the manifold (bank 1) is a notorious spot on FWD engines to go bad often.
