Yaris 1,3 petrol with hesitation problem

[medion65]

Thanks for the membership. Hope there are someone who can help me with my first Toyota ever. It is a 2000 Verso 1,3 petrol. It runs just fine on idle or maybe a little high. When i try to rev it up it hesitates but if i very carefully revs it up it becomes normal again. It also after a while throws the P0172 code meaning it runs too rich. Both O2 sensors are new, spark plugs and air filter also and i have checked for vacuum leaks everywhere. I hooked up the computer to see what kind of measurements the O2 sensors shows and it was some strange readings. The voltage on both sensors at idle is about 0,9V and google says thats ok but the strange reading is the B1-S1 short fuel term reads -20,3 at idle and the B2-S2 short term fuel shows "0" (no reading). Any help will be much appreciated. The emission is to high so i have to postspone the MOT until i can find the reason.