[Tcoat]

Originally Posted by tomato86

Well I took to trying to scrape around there again, the buildup is not as bad as it was when I did it, nothing new really accumulated. I'm not sure what it was but I'll continue to keep an eye on it. The bad smells aren't really there either.

I still have a small theory that says my former Amuse front pipe was causing it, only because there was an exhaust leak from the pipe not being totally flush with the stock header.

That is an excellent theory and if you mentioned that before then I missed it! Combination of dirt and soot would explain the slightly fluffy appearance in the pics.