When my spliced O2 started leeking vlotage the car would hesitate. Easy way to check is unplug it when the car is warmed up and see if the symptoms go away or not. Could have different results then on my 85 due to the limp mode adjustment.
But you can easily check the O2 with a multimeter. Readings are supposed to be from 0 to 1 V. If I remeber correctly, very close to 0 at idle, and when you floor it it should go almost up to 1V.
1985 190E 2.3L - a constant project.