What is this on my overpipe?
 

I have a JDL UEL catless header and pictured was my Private Label MFG overpipe. The thing rattled against the subframe like crazy despite all efforts against that, so I'm switching it out for a Perrin overpipe.

I had this overpipe installed maybe a few days and noticed this bronze stuff covering the flanges after uninstalling it, but only the overpipe flanges and not the header or front pipe. It also comes off if I scratch it a little hard. I may be wrong, but I don't think it came like that.

I used the GS gaskets on both sides. Was there a leak or what? I had no CEL (also have OFT stage 2 tune), I don't think I smelled a leak (I have a horrible nose all year round thanks to allergies), didn't feel any air coming from flanges after installing (although the fan shroud makes it kind of hard to feel little stuff).

Any opinions?

http://i.imgur.com/TFq8zYP.jpg
http://i.imgur.com/YobXdFE.jpg
http://i.imgur.com/Jme5lNv.jpg
http://i.imgur.com/sCyPlke.jpg
http://i.imgur.com/h6Zzlyy.jpg

Check your cam plate directly above the overpipe on the back of the engine and see if it's leaking oil?

I believe it a flux component PLM uses for quick welding.. Hence why it is inside too. or maybe an acid dip to clean off impurities or sealer for the weld

Most likely. Seems to be an organized portion so it would lead me to believe it's part of the unit itself and came like that from the company. Keep us posted tho if you find out any info.

I had the same thing on a PLM header years ago, I won't recommend them ever, but my comments and thoughts on there product are outweighed by the price.
You can see the dark brown stuff on flange here too.

Maybe magnaflux residue?

Thanks for all of the replies. I'm pretty sure it's a chemical PLM coats the end of their pipes in (inside and out) that turns bronze/brown with intense heat.

My cam plate wasn't leaking and I highly doubt there was an exhaust leak.

Like celek said, I wouldn't recommend buying PLM. The Perrin overpipe had breathing room between it and the subframe even after I wrapped it in a titanium exhaust wrap. The PLM was maybe 2cm even when pushing up on it to get it as high as it could go.

I kind of see overpipes similar to HDMI cables. It's all pretty much the same damn thing performance-wise. It's just how wide you want to go and how it fits that really matter.

Was there any tape on that area when you got it? Looks like burnt tape residue.