Odd problem
 

Recently I rewired my fuel pump and now I have over 13 volts of power going to it. However, I noticed now that the car has a slight hesitation but if I disconnect the O2 sensor, then it goes away. Do you think my O2 is shot or do I need to get a fuel pump with a higher rate of flow? Thanks.
BTW, it's S5 vert with full exhaust and intake.

More likely an 02 problem. I seriously doubt you need more fuel unless you have mods that would require it.

if you end up changing the O2 sensor, save a bunch of $$$ and go with the universal one. There is only one wire and it is real easy to install.