Barrels tent to speed up a little after they have had 100 or so rounds through them, so it seems interesting that you are seeing the opposite. Again, my opinion but I would get the barrel fouled again, 10 to 15 rounds to reach an equilibrium and see where you are at.
Do you use a chronograph?
I honestly prefer a fouled barrel, and only do a deep clean at the end of season, or if it's seen a lot of moisture.
After you clean with the KG product with brush and patch, I probably wouldn't worry too much about the residual copper, it's nearly impossible to get completely rid of.
Other products to try are Butches Bore shine, and Wipe Out or Patch Out if your not satisfied with the KG line.