Link ECU. Tune the AFR to a set point. Wideband indicates a certain mixture point. Later, go to the same conditions (rpm, load, temp, etc) and the lambda compensation is having to add fuel. I don't store any auto tune. Get back to that same point later, and the mixture is just fine.

Ideas? I'm thinking flaky fuel pump, clogged fuel filter... Could I have a couple revolutions of misfire on one cyl and not really notice it, thus making the O2 sensor see a lot of oxygen, even though there is enough fuel to burn it?

 

How much compensation is it adding? A couple percent could just be as simple as humidity or something, but a lot could be worth looking into.

Did you or Andrew end up driving that car home last night with no exhaust?

 

Maybe you need to recalibrate your wideband.