Why would my wide band be reading really lean cruising at 75mph?

If I let off the throttle and get back on it or give it more gas it rich-ens back up but then slowly starts to lean back out. /ubbthreads/images/graemlins/dunno.gif

I am probably the least qualified person to respond to this, but my guess would be that the ecu is recognizing a constant throttle input and might be going into a lean mode in an effort to get good mpg. I took a trip from denver to L.A. in my galant and was averaging over 35 mpg during one stretch. In the city I'm lucky if I can get 17 mpg.

How lean? Saying lean without a number is not telling much.
What does it go to at WOT? at light load? off throttle in gear?
What wideband? Is this the gauge or the log telling you this?

/brox

Is it going into closedloop? Is the O2 voltage cycling? Are you seeing any knock? If your chip has extended closedloop the ECU may be trying to stay in closedloop to save gas.