The residue is an interesting argument.
Many of them are due to the additives, specifically for copper fouling; but is related to operating pressure. The Extreme series looks clean, but causes hard carbon fouling. Comes down to stuff you can see and easily remove, or what you can't see, or remove.

The Traces were for illustration purposes, then Superformance loads were my very first loads. So they weren't tight, since I had done no development.
The IMR plant of GD was totally re-built this last summer.