Cat to Exhaust Gasket?
 

Anyone know where I can purchase one? Or a part number so I can buy one from the stealership? :)

Did you purchase your car used?
The gasket can be purchased/made at almost any decent muffler shop.

i have one at work i can toss in an envelope for the cost of postage if need be. just pm me if you cant find one.

Are you talking about the stock exhaust? If so, you will not see a conventional gasket. It is a metal ring that is permanently fixed to the end of the stock exhaust.

Well, I installed the HKS exhaust and I noticed that this section of piping didn't have a gasket (The part where three bolts are required).

Mufflers>Backpartofexhaust>Cat>Headers

In between the backpartofexhaust and Cat.

I thought the gasket was on the stock exhaust but I did notice it was permanently on there.

When I tighten the bolts, it seems like there is a space for a gasket to be in place.

I'm thinking that it would leak at higher RPMs without the gasket?

Hey Will - Sorry about this. I included everything I had. Perhaps I didn't have the gasket installed either??? I know I gave you a gasket or 2, but they were used - best to replace those anyway. Anyways, my apologies! :(

Nah it's ok.

I think what happened is that the OEM Exhaust has a gasket built in?

But either way I'm fine now, I just tightened the bolts alittle harder xD.

The water content of the exhaust will eventually find its way into the join and will start to leak. The gasket acts as a buffer between metal to metal contact.

Just uninstalled a T1-R exhaust today and put my OE exhaust back on. It seems as though the original Honda gasket was stuck to the cat. I couldn't get it off and it looked to be in good shape, so I reused it. I don't remember my T1-R including this gasket (just one for the resonator pipe flange), so I'm assuming it was OE.

It was one of those flat ones, shaped exactly like the flange.

Nope, the OE exhaust had no such gasket, just that metal ring that's permanently stuck onto the exhaust side of the pipe. Only the stock cat will mate to the stock exhaust using this ring. If you change the cat or the exhaust, you get that gasket.
What you saw is the typical aftermarket exhaust gasket at that junction. This is the one that came with my test pipe. There was also one for my Neuspeed exhaust and one for my Fujitsubo.
https://cimg3.ibsrv.net/gimg/www.s2k...1bd993846f.png