Ford Mustang Forum - View Single Post - Headers - ARH vs. KOOKS
View Single Post
post #13 of (permalink) Old 02-17-2016
SHELBY GT 350 Member
4.6L Member
S197 Member
JBert's Avatar
Joined: Jan 2011
Location: Central Massachusetts
Posts: 9,386
I'm pretty sure you always need to tune for headers to get the best performance.

As I understand it, the issue with the CEL / emissions / O2's is that most "high flow" cats don't work very well, so the rear O2's register that they are not working and then the rear O2 has to be turned off to avoid that code / CEL. But that's a catch-22 because you cannot pass emissions with the O2's turned off, all sensors must be reading "ready"

| 2010 GT coupe | Daily Driver with some Steeda and GT500 take-off stuff for the occasional track day
JBert is offline  
For the best viewing experience please update your browser to Google Chrome