Strangely enough, the shield does not appear to be broken loose at all. In fact, it is securely attached. The fact that I wrapped a couple of band type clamps around it and tightened them up pretty good and the noise still existed makes me think that there might be something else to this problem. The 'vise grips method' has the vise grips attached just to the edge of the lower shield (there's an upper and lower portion that is split down the middle of the pipe) and then resting on a bar that runs from the control arm area back about 2-3 feet. I suppose the vise grips are creating a king of dampening effect that stops the vibration. The fact that wrapping the clamps around the shield(s) didn't have any effect really stumps me. I'm guessing that the problem isn't with the shield but something very close to this area. Perhaps the exhaust manifold flange area where it connects to the exhaust pipe??? Maybe there's a loose bolt there and the dampening effect of the vise grips is mis-leading me into thinking the problem is with the shield? I guess my next step will be to get it into a muffler shop and up on a lift to see what the heck is going on in this area. Hard to really determine while laying on the garage floor... Anyway, I've owned 2 2nd gen Amigos and now a 2nd gen Rodeo and have had 2 out of 2 V6s (one of the Amigos was a 4cyl) with this problem, I thought that someone might have come across it before. The noise is so loud that it's impossible to not notice and again only happens around 2500 RPMs (a little less or a little more and it fades away). Also, only happens when moving (not while parked and revving the engine up to 2500 RPMs). When I finally get it figured out I'll update this post.