Popping on decel (throttle closed) is from too lean mixture screws or pilot jets. 3 1/2 turns is max, then go to next larger pilot jet and start over. Needle choice/shimming is for midrange tuning. Not an expert, everything I know I've learned on these forums, but when I turned my D-screws out 3 1/2 turns, popping on decel almost dissappeared entirely. Waiting for 45 pilots now. Someone smarter than me said to change only one thing at a time, or else you don't know which mod did what.
