I agree with phread59. Since you have the high speed needle well backed out I suspect that the problem is low-speed needle related, & I also suspect that it is too rich. When you do the pinch test and determine whether it is rich or lean, adjust the LOW speedle needle in 1/8 turn increments & test again. Another diagnostic test that has already been mentioned is monitoring HOW it quits when you open the throttle -- if it sputters & stumbles, the low speed needle is too rich, if it quits dead the low speed needle is too lean. When you are able to actually get the engine to run at full throttle, peak it then go back to idle & start the tuning process all over again. The needle settings are somewhat interactive & you need to have them both "in sync" for best performance.