If your alignment is/was off address that first. How have the brackets deviated from stock?

Another possibility is:

Look and see and if you have two different size groves in the Crank and WP pulley and if both of your belts have number starting in 15xx. Long post a while back on the PY site about this.

Use to be that there were a 1/2 and I think 3/8 belts but now there are only metric 15mm belts that fall in between. The problem is that the belts sits at different hights on the pulleys and thus rotate at different speeds and then squeals. Gates sells the correct sizes at Grainger but I keep throwing the alt belt. The better solution is to get the larger grove belt in a 17mm size. My brother has done this with his cars and works great.