Yellow dust inside one tailpipe

[davebrowne]

I have yellow dust inside the right-hand tailpipe? Like rust only lighter in colour? Any ideas what this is? 

[Steve Q]

Is it like a sulphur colour? 

[davebrowne]

Exactly!! Should I be worried?

[cliffcoggin]

I have never heard of such a problem so I did an internet search and found these:

https://mechanics.stackexchange.com/questions/48016/what-is-this-yellow-powder-on-my-exhaust-manifold

https://www.odyclub.com/threads/what-is-this-yellow-powder-at-the-top-of-the-muffler.372096/

which both seem plausible. As a chemist I can assure you it is not sulphur.