Stock exhaust manifolds

While driving the Duster I noticed it was a little louder than normal
(what's normal) :scratch: Anyhow on the passenger side exhaust manifold
has a bimetallic spring and rod that popped out of the manifold.
Is this a heat riser set up ?? Or is it some kind of smog equipment
for emissions. Can I pull it out and cap it? Thanks guys!! 8)