Kinda surprised when I asked if the catted version would throw codes and the answer was YES. I was told the O2's need to be deactivated or it would throw codes because the cats are high flow but not effective as oem units in scubbing O2. I asked why they were in the package and was told to help keep the smell down and to help pass a visual. I was reminded these are sold as off-road only.... I don't know about you guys but if I spend money on cats I expect them to work. If I ever have to pass a sniffer I would like them to perform their job. With that said, maybe I buy without cats or maybe another brand... ? ? ?

 

The same thing applies with any high flow cats I've seen. But I think Dynatech uses regular cats in theirs if that suits you better.

Besides that, you'll need a tune with any headers you install. The cats still function the same if the tune has disabled the DTC's.

 

Everything I've seen on the Magnaflow cats is they are damn near as clean as stock. Might look into adding them into an off road Y-pipe.

 

the biggest problem is the cats are moved farther down stream.Just get it tuned .Even if you add the magnaflow cats it will still throw codes.

 

Dynatechs threw codes on my 07 nnbs 6.0 as well

 

Exactly. Most cats are going to behave like this. I have the 1-3/4" catted ARH version, and it threw a code about 2 days after install. That being said, once I got it tuned and the afr was corrected, the smell went away immediately. I'm happy.

 

I've never seen a set of cats with long tubes not throw efficiency codes. Too far downstream, and not enough catalyst surface area inside. There is a reason why they flow as well as they do. More than likely, you will still pass a sniffer, they just aren't as efficient as the stock cats that are right up against the manifolds.

 

Thanks everybody for the information and advice. I was just surprised that even after a tune they would throw codes.....

In fareness, I must commend ARH for their honesty on expectations

 

You will still pass a sniffer. The problem is the rear O2s........the extra flow makes them think the cats have failed. These codes need to be removed in tuning. No big deal.

 

I had a pair of magnaflow high flows behind my pacesetters on my 5.3 in my Z71 and never threw a code...never tuned out the rear O2s and drove it like that for 3 years. Just my experience. But for the record, Id just buy the catless ARHs and not waste the extra money.