I had two DA50's, and here at 530 ASL I couldn't get the HS needle to let enough fuel in to get the engine to drop 100 rpm on the rich side using 50:1 oil, and the LS needle set properly......Put a WT 76 on them and I could drop the rpm's 500 or more if I wanted.....The only way I could get them rich at WOT was to open the LS needle till it burbled real bad. Then that compensated for the lack of fuel on the high side.....

chris may very well have a mis matched header/prop combo, but he may also be just starving for fuel at WOT.......Try opening the L & H needles 2 1/2 turns and see what happens....It may be extremely rich at idle, but that will let more fuel through at WOT.