You want to make sure the motor is fully bedded in and most of the pinch is gone before dropping any shims.
Stick with the stock set up of 1 x alloy and 2 x thin copper until you have say 7 - 8 litres (1.5 + gal) through. Then if you feel the need, drop one thin copper shim out and see what you think for your track and set up.

That sudden richness could be a plug on the way out. I have personally never experianced a huge change in performance or tune when my motors properly bed in, but that may have something to do with the run in procedure I use. They just get faster and smoother as I put more tanks through them. The tune doesn't seem to change - not dramatically enough to be readily noticed anyway.