o2 sensor question - code p0139
 

2001 Boxster

I had a p0139 error code. o2 sensor bank 1 sensor 2. Also my car hesitates on acceleration. I unplugged the sensor and plugged it back in and messed with a wire a bit. Hesitation got much better and the error code went away. Should I go ahead and replace the o2 sensor of should i investigate for injector leaks before i replace the sensor? Also if I should replace the sensor what is the part #? Before Starter Catalyst, Left or Right) or After Starter Catalyst?

PO139 code is an aging (dying) sensor. Don't understand why it would effect your cars hesitation on acceleration. The 02 sensor monitors the efficiency of the cat. Clear the code and do a spirited drive....and then check for the code again. Might go away and not come back.

The engine light went away after i messed with o2 sensor. Still i have some hesitation when accelerating

According to https://www.yourmechanic.com/article/p0139-obd-ii-trouble-code-o2-sensor-circuit-slow-response-bank-1-sensor-2

What are the symptoms of the P0139 code?

The engine may stall or run rough on deceleration if excessive fuel is getting in the engine.

The Check Engine Light will come on.

The engine may hesitate upon acceleration after a deceleration phase.

As you posted, that code is for the post cat o2 sensor. The post cat sensors will not affect how the car runs. Period.
They only monitor the condition of the catalytic converter.

Your hesitation is completely unrelated.