Can you post the numbers of the codes you had? I can't lookup descriptions. Front being lean and back being rich makes me think low fuel pressure, but I would expect different codes, so have you had other codes other than you mention? Have you any history on the fuel supply system? IE pump filter and pressure reg.
Try unplugging the MAFs and driving it. Should run way better, if it does not put a fuel gauge on at the fuel filter and see what the readings are. Likely two new mafs are in your future. Still don't see a reason for 4 being so rich maybe a bad or dirty flow pattern.
Those plugs indicate the front two cylinders on both banks are OK (grey/white ground electrodes and clean white insulator) and the back two are sooty with burnt oil, especially #4. Any oil in the plug wells? Or in the plenum?
I don't have a GT1 at my house. So I won't be able to do that until next week. I do have a scanner for my iphone.
It did pull a Lexus VVT performance sensor code (Bank 2) which I believe is a Crank Position Sensor. It is a generic code reader so codes are interchangeable on it. A CPS can cause multiple misfires and rough idles.
Mass Air Flow Meter
and.... should I consider doing the Crank Position Sensor?