I currently have a CEL on my HR with the ART pipes, but like the others here it was the primary o2s (the ones in the headers) throwing the code. The first time mine threw the code I found out that I had a major exhaust leak where the test pipes met against the headers. I (hopefully) fixed that a few weeks ago, but my CEL popped up again a few days ago, primary o2s again. Don't know what is wrong this time, and I really hope it's not another leak.

Because its the primary o2s I don't see how it could have anything to do with the bung length or whether there is steel wool there since those o2s aren't the ones throwing the codes.

 

The graphite gaskets are now discontinued and we now supply the ART pipes with Silicon RTV gasket maker. Silicone resists oxidation better than the graphite gaskets.

This may be all you need.

 

I had an exhaust shop fix the leak for me and they used some kind of gasket maker to seal the pipes against the headers. I'm not sure if it was silicone but I took a look under the car and it was a grey-ish substance. Anyways it seemed to work for a few weeks and now my CEL is back and I seem to have lost some performance (especially low end torque).

I gotta say I'm a little annoyed that I'm still (likely) having leaks with these pipes. I do wonder if my stock catback has anything to do with it: I notice that I can hear and see the stock y-pipe vibrating when I rev the engine from about 2.5K-3.5K rpms, and I'm starting to wonder if this vibration is contributing to the leaks somehow. I also wonder if the stock catback / y-pipe doesn't have enough flex for the art pipes.

I think my plan is to buy the TDX shockwave (mostly because its a sweet exhaust, but if it helps prevent another leak then that is a nice bonus) and then try to reseal the ART pipes when I put the catback on.

Tony, do you have any other tips on how I can fix/prevent leaks between the ART pipes and the headers?

 

Graphite holds up to heat better than Silicone.
As far as oxidation...

Graphite is best used where steam and process cycling is involved, to provide performance superior to the standard non-asbestos jointings.

Do not use graphite in environments where temperatures reach over 440 centigrade in the presence of oxygen.

So, oxidation doesn't pose a problem until your looking at 824* F!
As a reference..the RTV is approved up to 750* F.

 

In this application, the graphite gaskets fail (due to oxidation), the silicone does not.