<P>Matt, did you ever get to the bottom of this? My 03 Eddie V8 4wd does the EXACT same thing. I can't figure out what's making the noise, but I know it's load sensitive. Either that, or it goes away during the tranny shifts. My best guess is that the catalytic converters are broken up inside, and rattling around. The noise goes away at WOT.</P>
<P>I already checked heat shields, and even smacked the cats with a rubber mallet, but didn't find any noisy ones. My gut tells me it's in the trans, but the only thing I could think of is some sort of bearing noise, quite possibly in the converter.</P>