Cobalt SS Network - new guy from Missouri

Hey everyone. I'm new to the forum and Cobalts. I started working for BNSF couple months ago and need a new car cause my blazer is rough on gas traveling a lot. I was looking around Craigslist for a 05+ gas getter that was still sporty and came across a 06 Cobalt ss/sc 5spd. I never heard of a Cobalt coming with a sc or tc. So I started searching around and found this forum. I do have a some questions. First how reliable is the Cobalt ss/sc and tc? I'm wanted something reliable cause I'm traveling a lot. Second what are some things i need to look for when I test drive the car? Third what upgrades can I do to help performance without hurting gas mileage much? I do plan on putting and exhaust on. What exhaust is there that ain't too loud and doesn't sound like a pissed off weed eater? Thanks