FT86SF has an uncatted version of their header, maybe one day someone will test them and compare, if there is no difference, then your argument is moot.

And now JDL is bringing out their catted UEL, if the difference is nill, again, your argument is moot.

The only way the differences would be moot is if the design stays EXACTLY the same with the only difference being the cat. I know for a fact that the catted JDL UEL is a completely different design than their current uncatted UEL. At that point, the differences (good or bad) would have no way to be attributed to whether the cat was there or not.

It also comes down to tuning, if you are running the same exact tune on the same car with same timing. Stock tune is not valid here. Or perhaps run a degree or 2 more timing without a cat? Who knows.

FT86SF header is exactly the same catted and uncatted.

You have a bad case of selective reading if you think there are no valid arguments for wanting a catted header after reading this whole thread.

I read the thread in its entirety. The biggest concern people have is legality it seems like, and cat or no cat, an aftermarket solution isn't legal unless you had a failed cat. The other concerns are better rectified with other solutions. Not sure how that makes for selective reading.

This thread is filled to the brim with terrible assumptions and power comparisons that are most likely made via different dynos and different cat options.

What I'd like to point out is that with a catted option, while you might still make great power you are still introducing a restriction regardless of however little it might be.

For those who are looking purely for the most flow (notice how I didn't say power as the restriction might or might not be negligible) a non-catted design is still what should be chosen.

To answer the original poster comment, I feel like JDL summarized it nicely, cats are expensive and there isn't really much benefit you can garner from them that you couldn't get otherwise. As they still will only pass a visual perspective (smog etc), you can mitigate sound via after the header, there is not a cel-free guarantee.

Not saying no reason to buy a Cat but there are some reasons for going cat or cat-free.

oh also, California > every other state

To everyone here buy whatever you want, for any reason! Don't try to explain why you want it, just do it. Arguing is pointless, at the end of the day it's your money and your happiness.

We don't take kindly to your type around here. :bonk:

Really wish people would stop getting the misconception that just because it's a catted header, you don't need a tune....

Your ECU makes that decision, not you. Seen quite a few people already throwing P0420 thinking they can run stock tunes because the header is catted. Aftermarket headers change the flow regardless of a cat being there.

Yes, some of you won't throw a CEL, and some of you will. It's more about how you drive the car with it on a stock tune that will determine it. City driver? You probably won't see it. Highway driver? Yeah, probably a good chance you WILL see a CEL.

When it really comes down to it, your tuner can do a lot more with your car having an aftermarket header with better flow and a proper collectors.