more info:

yesterday I installed a new set of Denso IK27 spark plugs and they show at this way now:




just after 4 mi of driving. the one in the left is cyl 4 and the one in the right is number 1

it looks that cyl 3 is running really lean. I will do a injector clean during week.



I checked the WB controller on another engine I've with a WB since 4 years and in that car shows the correct AFR's, so it should not be fooling on the YB