MB C180 Kompressor P2188 trouble

Hi all.

im struggling with my 2008 mercedes c180 1.8 supercharged M271 engine and code p2188 System to rich at idle bank one.

on my live data at idle my 02B1S1 @2v 02B152 @

0.7v Mass air flow 4.2 G/S Long fuel trim 0% short fuel trim -21%

my thought is the 02 sensor one is faulty due to oil ingress in wiring loom from camshaft magnets leaking internally and capillary action through wiring to 02 sensor as there was oil in plug also up to ecu Large plug.

other than MIL the car runs and drives smoothly.

So far all i have done is clean as much oil from the 02, magnets and ecu plugs as possible with brake cleaner. this has helped with the MIL now it will stay off for 40 minutes to an hour of driving.

any mercedes guru on here point me in the right direction before i buy lambda, cam magnets and new wiring pig tails.

thanks