How bad would the car run without the secondary o2 sensor with the stock ecu? I'm looking to get a carsound cat put in soon, and have the aem ems on order (should be a week or two till it comes in) so after the ecu's in I won't have a problem with the cel. Should I just wait to get the ecu first and then get the cat, or just get the cat put on and live with the cel for a week or so.

 

The second o2 sensors does very little. From what I have been told it mearly monitors the health of the cat.

You can get the cat anytime you want, it shouldn't cause a problem.