[kbinkster]

I talked to Willy and he thinks that it could be flame splashback, as well, but that there might be something else contributing to it (to make it hot enough for the carbon to stick).

If you turn on your outerfire, and leave the centerfire preset to where it was, that outerfire could take oxygen away from your centerfire, possibly starving it a little for oxygen. You can turn the oxygen just a little bit on your centerfire to get some oxygen back to it and that should help.

So, try working a little further out and see if that helps and then try opening your oxygen a little bit more on your centerfire when you turn the outerfire on.