In CA, Magnaflow only sells cats through dealers (who charge $1100 just for the part), and Magnaflow has no cats for a 2007 Grand Prix. Thanks, though.
Exhaust shops, like Meinke, won't fix it because they can't get an after market cat for my car. It's frustrating. I need to register my car through my dad in Arizona, and get it fixed and smogged there.