gains from catless headers?
 

Is there any noticeable gains to be had by running a catless header vs. A header with a high flow cat on a N/A application on our cars

Yes

That's it?

Yes, there are noticeable gains to be had from a catless header over those from a catted header, all other things being the same in a controlled environment. Cats are inherently restrictive and removing them will increase exhaust velocity and when properly tuned, the engines performance figures can be increased significantly.

The reason nobody else is responding to your inquiry is because there is already a wealth of information and a bunch of threads directly related to your question on this forum.

The search feature is your friend. :)

I would say it depends on the header. With the P&L header there was a 4-5 hp difference.

Atl was referring to higher hp application. Not the standard na bolt on stuff.

No, I was speaking in general which also applies to n/a applications. Most cold air intakes yield around 5whp gains and everyone who installs those say it's noticeable, which is literally all the OP asked about regarding headers.

In na applications cat vs no cat is not a material difference.

Thanks alot

Stock header vs Rev Works UEL on my car after tuning yielded 180whp (4th gear). I think it was about a 15whp gain over stock. The only other change was a K&N panel filter. VERY noticeable change in power.

All of the NA header comparisons I've seen have had a few horsepower variance, but maybe 5whp tops between aftermarket catted vs uncatted. The main things to consider are your state's emissions laws and the sound you're looking for.

The difference really isn't in the restrictiveness of the cat, since a good header with cat would hopefully have a pretty high quality cat in it. The real issue is that it limits the ability for the manufacturer to get the right runner lengths that really give this car the proper design. So yes, there is a difference, and it's most likely design related and not cat related, from what I've read. And yes, this is talked about extensive on the forums, and I'm kind of tired of the 4+ new header question threads a week that are all clearly documented in many threads. Read the stickies.

thanks I have been on here a long time trying to get info and I totally overlooked the stickies

Thanks for the not giving me a non pretentious answer like some other people.exactly what I was looking for