This is happening on a 2002 Pontiac Firebird 3.8L V6 - I have a GENERAL question regarding these codes.

DTC P0133 HO2S slow response bank 1 sensor 1.
DTC P0153 HO2S slow response bank 2 sensor 1.

Does this mean its taking too long for my O2 sensors to heat up?

Also I have an O2 sim in the rear, can this be causing this code to trigger?

 

No to both questions.

The codes set when the sensor's switching between rich and lean is too slow. To control the A/F ratio, and make the cat work, the PCM swings the A/F ratio back and forth rapidly from slightly rich to slightly lean continuously. The cat stores oxygen when the mixture is slightly lean, and uses the stored oxygen to oxidze unburned HC's and CO when the mixture is slightly rich.

Slow switching may indicate the sensor is nearing the end of it's useful life. This would not be caused by the after cat sensor, but low oxygen storage is what the after-cat sensor is monitoring. Most likely replacing the pre-cat sensors would eliminate the code for low oxygen storage being set by the after-cat sensor.

 

See the thing is, it's saying BOTH of my O2 sensors have gone bad and they BOTH went bad at the exact same time. These are Bosch units from Autozone and they havent even been installed for 6 months / 10k miles... Why would they go bad so quickly?

I was running lean for about 400 miles after their install but I got that resolved relatively quickly with a new fuel pump. CURRENTLY I'm losing antifreeze through some mysterious way. No visable leaks, no odor, just 1 week later and a whole quart is gone. Car still cranks and drives fine. I think I have a bad intake gasket - is it possible that coolant intake could cause this problem?

 

O2 sensors can be contaminated with silicates. Conventional green ethylene glycol coolant contains silicates. That's why GM switched to Dex-Cool ethylene glycol, because it does not contain silicates.