I posted the question on the 12 valve forums, then had a member cross over to put his two cents in from the 24 valve forum, so I thought I would present it here as well. My 03 is almost sickly quiet, my 91 has a smooth, yet firm knock when it idles and just off idle, sweet music. I have heard some second generation trucks that really bang at idle or just off idle. You guys have a theory? 12 valve or 24 valve have the distinction of the loudest knock? I know the 24 valve sounds a lot busier! Glen