[Hethj7]

Code 91 means that your drivers side O2 sensor is reading lean. Since the right side is reading normal, that rules out a vacuum leak or a fuel pressure problem. Likely causes are a bad O2 sensor, or a bad injector in cylinders 5-8. If you don't have a miss, it's the O2 sensor. If you do have a miss, do a power balance test, and see which cylinder it is.

This is from PKRWUD, who really knows his stuff. When I had the 91, I replaced my o2 sensor and that cleared the code. Sorry, I don't know about the others.

Serach the site for posts about codes.....most of these have probably been covered at one time or another.