Engine Error Codes Help - New Owner: 2nd Gen 4x4 3.0 Manual

Hey everyone, this is my first post to the forum so if I do something wrong please correct me!

I'm a new owner of a '92 4x4 3.0L Manual, it has a 4" lift kit, 33" tires, aftermarket rear diff lock (pretty sketchy so will probably disconnect it soon). I'm running engine diagnostics to try and figure out what's wrong with the vehicle (the guy I bought it from has no idea, this truck has been through a number of shady owners from what I'm gathering). Codes I've read from the diagnostic system are 12, 14, 41, and 71.

I had a new catalytic converter installed 5 days ago, so curious if this may have something to do with the code 71 at all. As for the other codes, the engine turns, shifts, drives, brakes, and accelerates without any issues seemingly. Feels strong when driving and has good torque, with no alarming or strange noises. The idle does scare me a bit though, as it fluctuates drastically between 1400 rpms and 700 rpms. Could this be a timing issue or would it be related to codes 12/14? Newbie here so please, any insight at all is helpful. Where's the best place to start?

 

welcome