Around Nashville and Chattanooga you need to pass visual, safety, and no check engine lights. few counties here and there are about the same standards but Knoxville just got in trouble about putting out too much pollution so I bet they will be picking up the same as well. I live just outside of Knoxville where we don't have testing and I have never had any problems with police in places that do testing. I run off road X-pipe and a simple 2 chamber muffler on my 95 GT. Location of where you are at would help some but I wouldn't be too worried about typical mods.