question me and my friends were arguing about is i got rid of my cat on my 08 si it would affect my a/f and i would have to get re tuned since the sensors would be positioned differently on the test pipe because i will have a bung welded for the primary and secondary. note: im turbo so if it effect my a/f i would needa get retune but i told him that it wouldnt affect anything any have input on this? also should i just eliminate the seondary o2 or should i have a bung welded for it since i dont think it will effect much correct? some one help me im a noob to this kinda of stuff.

 

Chances are you'll need a re-tune. Get a wideband to know for sure

 

x2

 

You should probably get a tune when making any changes to your setup. Do you have to? No but if you want your car to run safely and to its fullest potential, then get a retune