Odds are that you will need to install the O2 extensions downstream, that's where I'd start.
The shop that tuned my 2010 Challenger SRT8 6.1 to get it to pass emissions had to install 2 of them on each exhaust pipe so it wouldn't trip a code for the O2's.
From what I've heard, the extensions are usually required with long tube headers.
Mine has Kooks long tube headers and Kooks hi-flow cats.
If an emissions test isn't required they can turn off the rear O2's and it will run fine.
That's what had been done to my car by a previous owner.
Alabama doesn't require emission inspections, where I live in Missouri does.
Last edited by SNK-EYZ; 09/23/21 02:31 AM.