I have an OS 160FX with a Perry VP30 and it runs really well with no adjustment to the pump at all. I did have the turn the low end needle in to the point of only being just over one turn out from being fully closed. My engine seems to change tone like it's four stroking when I reduce the throttle from a cruise flight to 1/4 throttle or so when I slow down. It idles and transitions great and the top end is just a little rich. Does this sound typical or does it sound like the mid range might be a little rich?