Engine Code P1133 ,???

Car is a 97 lumina with 3.1 , and 185 k . Engine light come on, it registered one code P1133 which translated to
"Bank 1 Fuel Control Shifted Lean ( FAOSC) ". Anyone want to explain? I drove it another hour to get home, and it ran well. Thanks in advance.
What I got from internet searching;;;;;
Fore-Aft Oxygen Sensor Control, or FAOSC. With a healthy pre-cat at a steady idle, ...

aul, I can't get into it in detail, but it's a feature called Fore-Aft Oxygen Sensor Control, or FAOSC. With a healthy pre-cat at a steady idle, the rear sensor reads about 0.6v, which is slightly rich. This makes sense because the cat brick is absorbing your excess O2. Now what happens if that point starts to drift, assuming in this case all the upstream fuel control pieces are working correctly? If it drifts lean, <=0.5v , it could either be the cat going bad, or a front O2 sensor shift. If it steadily drifts even more rich, >.6v , then the cat is obviously OK, so maybe the front O2 sensor is drifting rich. FAOSC logic isolates this shift, and then uses the rear O2 input to move the front O2 sensor lean/rich switch point back to stoichiometric.
So.. I replace the front O2 sensor on the cat ?

Don't over complicate this. Check this link for the info. http://service.gm.com/gmspo/mode6/pdf/1997/97c31M_W__yE.pdf