1994 F150 - 5.8L V8 - Automatic - 256k miles

Hi guys I'm having some minor annoyances. For the longest time my thermostat was stuck open and my truck never reached closed loop mode. I fixed it back in February and immediately I got a CEL after driving at operating temperature. The CEL on comes on only when driving. If I let the car idle to operating temperature then nothing happens, but if I drive a mile or so down the road the dadgum thing comes on. I've pulled the codes and got 172 and 565. I've cleared the codes and they came back. I know I followed the right method for clearing them because I had a bunch of random codes for temperatures out of range that went away.

172 - Oxygen sensor not switching – system is or was lean – Single, Right or Rear HO2S – Fuel control
565 - Canister Purge 1 solenoid/circuit failure – Solenoids

I've checked my coffee can and vacuum lines for leaks and didn't find any. I also checked the fuse for the O2 sensor and it had continuity. The truck runs great and can give my mustang a run for its money, so without a discernible performance impact I'm really at a loss for what is going on. I do notice that I'm getting about 10-12 MPG but I haven't really kept up with the fuel economy until now so that may be normal. Anyways, long story short I have no idea where to begin. I would hate to just buy random parts (O2 sensor, etc) if the issue could be somewhere else and these are just symptoms rather than problems. Has anyone had this issue before and could point me in the right direction of where to begin?

Thanks for your help!

 

The 565 code is a KOEO code only and you can not clear the KOEO codes.
This an electrical code:
Possible causes:
-- Open harness (VPWR or CANP).
-- Damaged CANP solenoid.
-- Shorted (power to ground) harness.
-- Damaged Powertrain Control Module (PCM).