Stupid Question
Use the front O2's. Either get O2 simms for the rear ( if you are not running cats ) or don't plug anything in.
If you do not run the front O2's, car will run like crap.
If you do not run rear O2's, you will get an SES light. However, it does NOT affect performance.
Or, have them weld the bungs into the cats themselves. FLP did this for me for free when I ordered 3 years ago.





