[tjokke]

i have a fault code on mijn 986 s 2003

P2096 Post Catalytic Fuel Trim Bank 1 System Too Lean

i replaced the post cat o2 sensor, but the fault comes back after 80 miles

when i read the o2 sensors value with started engine

bank 1 post cat sensor stays almost all the time at 0.1 v
on bank 2 the sensor is 0.1 at idle, on acceration it goes up to 0.6-0.8
but bank 1 remains at 0.1

when i go off trottle both the sensors go to 0.000

both the o2 sensors are new,
the dealer thinks i have a bad cat, but he is not 100% sure

take the gamble en replace?
or are there things i can check myself?