P2A00 Code after HFC install. Need some input

jockeus

Hey guys, I don't post alot here, but am a frequent reader. It's an awesome forum with alot of helpful people. You guys have helped me alot in the past with all the good DIY's and helpful posts.
This time however I need some input on my situation.

I installed the Berk HFC's a while back, and one of the O2 sensors gave me trouble. It didn't want to come off the stock cat, which resulted in some abuse and damaged threads.
Since I didn't want to buy a new one, I tried to install it anyways, and it seemed like it worked.

After a while though I got CEL come on. Torque told me it was "P2A00 - Powertrain" "O2 sensor circuit range/performance bank1 sensor1".
To my understanding this indicates the precat sensor on the passenger side is at fault?

Anyhow, after I got the code I started monitoring voltages on the post-cat sensors, and noticed that the one with damaged threads (on passenger side) consistently had lower voltage readings than the other.

Yesterday I switched sides on the sensors just to see if the readings would change, which they did. I now have consistently lower voltages on driver side o2 sensor.

I haven't gotten the CEL again after the switch, but I guess it's just a matter of time.

A thing to note though is that I recently started hearing a sucking/blowing air noise when letting off the gas at 1500rpm. I've had the CEL for a couple weeks and I noticed this sound maybe 1-2 weeks ago, not sure if it was there from the start, don't think so.

What do you think is up?
Bad precat O2 sensor? Postcat? Vacuum leak?
According to the service manual the postcat sensor is not a possible cause.
Should I keep driving until I get the code again to see if it switches to bank 2?

I am extremely grateful for any input on this, if you need any more info please let me know. Thanks!