I'd just leave this sub-forum here. Once the mods start coming out, you'll have to split performance mods into subsections anyway.
Even a disabling-the-coolant-through-the-throttle-body modification (assuming the Caliber utlizes this for environmental reasons) would be considered a peformance mod, and this section will fill up fast with questions and whatnot. But then someone putting in urethane bushings in their suspension may think that's a performance mod too.
I would actually recommend that as the forum grows, you split the "modifications" forums into Powertrain and Suspension as their own descrite forums.