Finally got my HHR up on a lift and discovered what was causing the rattle. When I added the header and new Catalytic Converter, I inadvertently lengthened the exhaust causing the tail end exhaust hanger to pull everything upwards, creating the rattle. So just need to shorten a bit and weld it back up. Last photo is where the muffler is making contact.

Robert

 

Just touching the heat shield, may be just a tweak with a pry bar, and cure that rattling

 

Mine had a heat shield over the top of the pipe as it rounded above the rear axle beam area.
I used some stainless scrubber pad between the pipe and sheet metal shield, and stainless wire to pull it tight in a couple spots, eliminated that rattle.

 

Necessity is the mother of invention.
Fasten 'er back in or pull it off and toss it either way
Git 'er done.
Simple is better bumper sticker should be issued.