I had this same issue. After you verify its the timing by runing it for a few minuets with acc belts off, double check the 3.5-5.5mm spacing for the auto-tensioner. I had mine way too tight some how. Also I noticed on mine that the back plate to the timing cover aroung the itiming idler pully at lower plenuem was bend out (toward the timing belt and pully) and just barely touching the idler pully. These two issues made my car sound just like a supercharger.