just noticed a problem HELP.A/F

[foggy]

It is working fine. It will go from rich to lean back and forth under cruise. It is showing you the computer is constantly correcting to keep the engine in the best mixture for economy and emissions.

[farmtruc]

GM has this thing cause DFCO, decel fuel cutoff. The pcm cuts fuel while coasting and no throttle, so you'll notice the gauge go lean, that is perfectly ok. During crusing, it's ok for the gauge to go up to 17, it won't hurt anything. The important part is to be sure the gauge goes rich under boost.
I run my av at 15-17 a/f ratio while cruising and it gets great mileage and has been fine for about 45K miles.

Think about this, GM doesn't allow some of their trucks to richen up over 5K and after 5secs of wide open throttle.

The sensors seem to be more accurate if they have a nice steady flow of air going over it, and steady stream, like under throttle.

hope this helps,
allen