I heard a rattling sound going over some bumps, and found the heat shield under the exhaust manifold was dangling.. looks like some of the bolts failed. So I clamped it back on with a worm gear clamp. Wish me luck!

 

Likely the bolt holes on the heat shield rusted out. The nuts on the studs should be easy to remove. I found these washers to work well to reattach the shield.

https://www.napaonline.com/en/p/ATMN90796502

These are sized to press fit over the studs and grip the stud. I used a needle nose pliers to break off the tips at the center and slip the washer over the stud and reuse the nut.