can hear it when reving up around 3k with no load , haven't noticed the sound under a load. thought it was the pulley cover being hit by the belt. don't think so. its a 1776cc, mild upgrade, mostly stock, 34 pict solex.4 into 1 header with a quietpak muffler. runs well. little deiseling after shutoff sometimes. the rattling noise is new-last couple of days.seemed to get better with warming up the other day-but not tonioght. sounds like a rattle inside the exhaust- down by where the headers merge. any ideas?