This may sound like a dumb question but I have often heard people use the phrase "throwing a CELL". What does that mean? Can it happen if with just replacing my stock exhaust with an aftermarket Cat-back?

 

Throwing a "CEL" = Check Engine Light.

As long as you don't remove the O2 sensor from your exhaust you shouldn't throw a code. If you do happen to throw a CEL while replacing your exhaust you should reset your ECU. You do this by pulling the Back up fuse in the fuse box under the hood for a few seconds or by disconnecting the (-) battery terminal for a few seconds. That should clear up the CEL and your good to go!

 

Also if you get a (Test pipe) in place of your converter like I did. The rear o2 sensor ( if located in or behind cat ) will show to much flow which will cause CELL to come on. to correct this you need to buy an spark plug non fouler. Screw this onto you o2 sensor, then screw the whole thing back in to o2 sensor bungle. This will pull the o2 out the exhuast stream enough to not set code. Works great!

 

I'm not sure what the amount of flow has to do with the O2 sensor? But if your spark plug non fouler thing works in the Mr. bungle for an easy SHO2S test pipe hack 2U. What size non fouler did you buy to fit the Accord O2 Sensor?