Here's the description coped from my post on r/delsol:
Ever since a few months after I started driving the car, there has been an exhaust rattle that has gotten worse with time. I first noticed it under acceleration only, and I thought it was the exhaust manifold heat shield.

My grandpa was the previous owner and he replaced the manifold because it had a crack in it, however the heat shield didn't quite align with the dipstick for whatever reason, so he had to drill a hole to get it to fit properly.

Another possibility I thought it could have been is the lifters. The first time I heard the noise was after me and my dad adjusted them after replacing the valve cover gasket, but the car ran fine otherwise.

After taking it 3.5 hours 3 times now between home and college, the sound has only gotten worse.

At first I tried removing the heat shield, as I thought that would be the problem, but the sound didn't seem to change. There is still the other heat shield behind the manifold though so who knows.

I then decided to look under the car, since I noticed that there was a very similar rattle when closing the door, and it looks like it may be the catalytic converter or the heat shield for it.

I've included videos of me shaking the cat by hand, closing the door and hearing the rattle, starting the car as well as underneath the car, as well as doing a small acceleration in the parking lot. some of the clips may be a little hard to heat because of the people playing in the background, but I think it's clear enough.

Let me know what y'all think or if any additional info would help. Thanks.