After installing headers, new cats and catback, the car is running extremely sluggish. I also got an SES. My question is, des it matter if the O2 sensors might have gotten switched, meaning the front sensor on the rear and vice-versa?? Not sure if it happened, but is there a difference and does it matter??? If there is a difference, how can I tell the 2 apart??

 

the plugs are different for the front 02's vs the rear so I dont see how you could have switched them.

BTW with headers you have to delete the rear O2 sensors, even if you are still using CATs

 

it could happen if you are running shorty/mid headers (i believe the driverside downstream and the passenger side up stream could get crossed...cant remember).

the up streams should have a flat type connector and the down streams should have a square type connector.

and yes if they are switched it will cause the car to mis bad, the ses light should flash also.