how much deflection are you adjusting your belt to? Remember to check the deflection on the side with the longest distance between pulleys. And if its a twin belt setup check between the two. More times than i can count i had customers complain that they couldn't get them to stop squealing so i was forced to take them back to single belt. They are an absolute pain if they wont align exactly. I had a car once that i really considered going to a gilmore drive simply because i couldnt get rid of the squeal of satan