well I'm going through the same problem myself.I had to replace the tensioner because I torqued it to much and the shaft was bound up.Most of my noise is gone except when I shift gears, once the engine reaches the rpms to shift it does the rattle or I can play with thottle at highway speeds and make it do it.I've looked at everything when I had the cover off and checked ok there was no wear on anything cover/oil pump drive/crank gear.It almost sounds like the chain is slaping the metal backed chain guides but they looked brand new and I've been driving the truck for a year.I feal your pain,it's driving me nuts if I can narrow mine down to something I'll let you know.