As a general rule, you want your Air/Fuel Ratio to be 13:1 or so. My car belches black smoke even running at 14:1 and dipping down 13.6:1 in the upper rpms. It's supposed to run that rich. If you don't like all that smoke and feel like burning your engine up you can have someone take out fuel by programming it.

 

When my cat on my old camaro clogged it just kept going off and if i got it started it would not even idle right. As for O2's, had one go bad on my Caprice, got an SES with a code for which sensor went out, but didnt get the problems you described.

 

ANYONE........ANY other suggestions????

 

Most possibly, SES light on highway were due to misfire. Please check all wires again, before anything else. It's common to burn them especially after plugs change. If you were running rich for a long time you can damage your O2's and fouled plugs. That will cause you running even more rich. Then, get it scanned. Sorry about that, but It can be time for a new opti too

 

Yea, let's start with the most expensive thing first. Rip off the damn catalytic converter and drive it. It won't hurt it, it'll actually help regardless. Might as well do something free instead of spending well over $300.