P-0139 Error-Help Needed

I recently put a new magnaflow exhaust with a magnaflow cat back and when I was done a week or so later my check engine light came on. I took it to my friends shop and had him run the codes and it said it was an O2 sensor. I purchased a new O2 sensor for the cat and had it put on. A week or so later the light came back on and had it read, was the same thing. The code is P0-139 oxygen sensor circuit slow to respond bank 1 sensor 2.

I am wondering what I can do about this because there is nothing wrong with the car it runs better than it did before but I can't stand a check engine light on. When I reset the code it will stay off for a little while but comes back on within 100 miles

Is there a way to bypass the sensor or a different O2 sensor I need to buy?

Thanks for any help in advance.

Cory