I took my cavi to the exhaust shop the other day and the guy was looking at my current system and I have 2.5 pipe with a inlet hole in my muffler is 2.0!? so he was thinkin of maybe putin a camaro muffler with 2 pipes, Just so happens I have my old setup from my camaro with a flowmaster muffler. My question is has anyone ever done this? And would it sound ok?

Yes it has been done, and how it would sound is relative to your taste. If you have a full system - header and high flow cat included, it will be much louder than just a cat-back. Adding a long-ish resonator will reduce raspyness and quiet it down a little.

Also the model of camaro muffler you choose will make a difference in sound - is it an OEM replacement or a flowmaster or an slp loudmouth?

I do have a longtube header, high flow cat and 2.5 catback. The muffler that is on the camaro system is a flowmaster. I am just wondering if its going to sound deep or raspy? I have the 2.4L

it will sound decent but I would HIGHLY suggest adding in a resonator that is 18" or longer to reduce any unwanted sounds...