I was driving to work and all of a sudden my exhaust got extremely loud as if I had an open header. Then I noticed significant power loss. While I was letting the car warm up I noticed a rattling sound from under the car, near the back side by the tires. I've heard this sparatically while driving since I bought the car a few days ago.
93 Del Sol Si

I'm guessing either my cat or my muffler went. I have a full Apexi WS2 system on my other del sol so that's not the problem.
My problem is I have to fix this tonight in the cold rain so I can have a fully functioning car for work tomorrow.

If I pull my cat and replace it, it could still be my muffler. So would it be better for me to pull my muffler, test drive it without it on and then see?

I'm just trying to figure out the most efficient way to do this so I can have my car for tomorrow. I've ruled exhaust leak out as the main issue because I don't think I'd have this much power loss. I'm assuming an exhaust leak would just be caused by the back pressure of the system being clogged somewhere.

Please help, It's much appreciated! Thanks!

 

Seafoam and look for the leak.

If no external leak then perhaps the cat is clogged.

 

Textbook plugged cat. Drop the exhaust at the header and look

 

Sounds like the cat. Remove it and test drive.