About the richer reading when letting off. Yes, I too get the 25 afr when letting off enough for the tps to cut the fuel to the injectors. What I'm talking about is a barely perceptible letting off of the throttle, just to maintain the speed of the car going downhill, not a letting off of the throttle til the tps sees fuel cut to the injectors.

Hmmm, maybe it is just my outfit. I'll try another when I get a chance.

 

I know exactly what you mean with the richening.
The cars run pretty rich at idle and through the midrange. It's only in closed loop at about 1/4 throttle, if you let off a bit, it goes out of closed loop and into idle mode... where it runs rich.
Do you see the cycling of the mixture during closed loop on the wideband? Just wondering if it's damped so much you cant' see that... If so, I'd remove the capacitor that damped that signal.

 

Yes, in closed loop the last digit cycles about four times a second. On the wideband.
When the car is plumb cold, it reads in the 11's and low 12's, and then the temp gauge rises and I can be toolng along at forty or whatever speedlimit and it'll be in the high 14's as I clump along, sometimes playing at the low 15's. Full blown throttle though, it goes in the low to middle 10's then to 11 plus or minus .2
I guess I'll buy a EGT gauge to go along with this. I wonder if their sensor will fit in a O2 bung?????