It sounds like you've done everything right. So now you have to double check some of the things your doing. Possible your adjusting the wrong valve? Recheck to make sure you have the intakes and exhaust matched up in the right position on each adjustment. Possible the set screw is coming loose for some reason on the one lifter your having trouble with. Check for bent push rod. Check for lack of oil on noisy lifter. Uh... I've run out of ideas. Cecil...