Well Their is always K&N air intake to start with. Then you can do exhaust work ,like high flow cat, The bigger diametar pipe,and new muffler really won't make your car faster but you can change the sound of it. OTher simple things you do is remove the maf screen in throttle body. You can also go from 195 t-stat to 180 t-stat doesn't really give you whole power better will make the car runn coolerThen if your really serious you can upgrade internal parts inside the engine to make them lighter and stornger. You could also work on trannsmission by putting shift kit, Then tranny cooler to make run cooler. You can also mod pcm programming by putting new chip. Then you can also run better spark plugs. This thread will problem be moved shortly to the section about mods.
2007 Dodge Caliber v4 5714 miles(cvt) tranny)
2002 Malibu 3100 117000 miles