Pls help me ID this engine rattle coming from driver's side

2000 Silverado 5.3 Z71
This rattle is almost definitely not: catalytic converter, piston slap, intermediate steering column, joint
When I crank my truck, and especially when I rev it up, I hear this faint rattle
type noise that sounds like it's coming from the driver's side engine compartment pretty close to my legs. The noise occurs whether moving or sitting still.
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Probably the header heat shield(s) for the plugs. I've taken a drift and a hammer and tapped the rivets back into the headers with out any problems. But that was on the passenger side of a 5.7.
It could also be the springs on the exhaust flange bolts, broken one at least.
Cheers
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