when i bought my car it already had a loud magnaflow on it. what i want to know is how would i tell if the entire exhaust was done and not just the muffler?

 

Look at the pipes underneath. You should definitely be able to tell which pipes are different. See how far towards the front the magnaflow parts go, and that will tell you just how much of the exhaust was replaced. Typically, it will either only go to just beyond the back wheel (axleback), or it will go all the way up to the Cat (which is what you want)