Good morning everyone. This is my first post here. I am having a problem with my Stihl BR 420 Backpack Blower. It starts and idles fine, but at high rpm, the only way I can get full power is to adjust the choke slightly (towards starting - closed position). I have checked my air filter (even tried to run for a minute without the filter on) and have checked the screen on the muffler, and neither seem to help. I have also tried to adjust the H and L and TA set screws on the carb, but no help either. If anyone else has had this problem or has an suggestions, please let me know. I am not super mechanically inclined, so please excuse me if I am not giving the appropriate mechanical terms.