Mike,
True, the idle mixture screws will not help the 3/4 throttle problem but like splodge has figured out, he has two sets of problems. The popping on decel should be helped by adjusting the mixture screws. The 3/4 throttle problem sounds like it's too rich. I had the same problem when I put on new pipes and was making adjustments. It was too rich and if I opened up the throttle it would bog down. If I slowly crept up to speed then it would still break up once I hit 60 or so in 5th gear (on a 16 tooth sprocket).
Jon,
Like Pat said, handle the problems one at a time. I'd set the idle screws to 2 turns (as a baseline) and start working on the jets. Once the jet problem is handled, then adjust the mixture screws so that you're not popping anymore.
