First ride with newly installed Boysen power reeds in my 2000 KDX 200. Bike has a FMF Gnarly desert pipe on it, otherwise stock. The bike definelty has more off-idle pull now, snappier out of corners. Motor is happier to lift the front wheel on demand. I left my jetting alone from before, seems to be okay. Maybe a bit richer? Top end power seems to be the same. Not too bad for a $25 mod.
It should effect the pilot jet, you said a little rich go down one size and 1 1/2 turns on air screw. 48 is stock with pipe and air box mod 45, and with the new reeds 42 should be spot on.