Did mid-seaon cleaning...

So I'm curious what you guys make of this. I did a quick cleaning today to make sure I don't burn my house down during the storm tomorrow. I know I've snuck in a few wet pieces this season and expected some buildup. I did find buildup, but it was all in the single wall pipe and wall thimble. Once it hit the chimney, it was clean as a whistle. I'm not sure what to make of it. My chimney is a 6' class A insulated thingy. I try to keep the single wall temp between 350 and 400, but I know it has slipped lower with the wetter stuff.

I'm just not sure how to interpret my findings and how to address it. There was only minimal buildup in the single wall pipe, maybe 1/2 cup total in 4' of pipe, but I don't get why it was so dirty and then suddenly clean outside. Thoughts? Any ideas of adjustments I can make to have the inside burn as cleanly as the outside?

That is very normal. Good job!
The single wall pipe gets more build up because it cools off so quickly. The chimney is insulated to prevent this from happening.
Switching to double wall connector pipe would be the only way to eliminate this. As long as you have no more than an 1/8" of build up your fine.

This the reason that a chimney liner should be insulated.

Okay, as long as that's normal it works for me.

Could be a slight leak of air there to cause the dirty buildup. It does not take much. Introduce the colder air there and it can turn black quite fast. But it sounds like you are good to go.