you can buy mufflers for cheap...
or just do a res delete and put in a glasspack. 30 dollars for a glasspack at advance auto parts/ wherever.
alot of people dont realize this platform isnt good for making power. sure you can make power...but at what cost? and it sounds like you need this car for your job. i would just put an intake and headers on it. get an aftermarket PCM. call it a day with this car.