420A Where should one put on a non-fouler? Before cat delete or after?

[Ethenp23]

I wanted to gut my cat on my 1995 eagle talon but don’t know if I should put the none fouler on before or after I gut the cat I was just going to gut it out and if it throws a cel then I’ll buy the none fouler because I didn’t want to waste money for no reason if it won’t throw a cel

 

[DSSA]

After. The point of it is to read lower A/F numbers *post* cat, to verify that the cat is working.

 

[1990TSIAWDTALON]

Spot On!
The only thing the 2nd sensor looks for is a lower # than the first sensor.

 

[BLACK'98DSM]

Have you looked into buying a test pipe instead of gutting the cat? You'll see better high end hp gains and less low end torque loss.