I find that my belt squeals largely depending on the alignment of the alternator pulley to the crank pulley. I found that the order in which you tighten down the alternator can slightly change the pulley alignment. As previously mentioned the belt needs to be fairly tight but after I adjust the tension I lay a level (any flat piece of metal should do) across the face of the pulleys and check to see how close they are to parallel with each other, if they aren't real close then mine squeals. You will probably have to experiment a bit to see which bolts twist/torque things which way but it does seem to make a difference.