The low speed needle controls about 80% of the throttle travel mixture control so it influences most of the fuel economy or the lack of it. When I lose or think I have lost the needle settings I richen both needles a little, then peak the high speed needle, richen the rpm from peaked down about 200 rpm. Next I procede to lean the low speed needle 1/8 turn at a time checking the idle and transition and high speed setting after every other change, one of the lowspeed needle changes will make a greater change in idle rpm than the previous ones did, now you are close, now set the LS needle for the best transition. I prefer to sacrifice a little idle speed in favor of a better transition as in I settle for a 100 rpm higher idle speed to get the best transition. It's the better trade off if a trade off is necessary.