Need help tuning my car PLEASE HELP

hey guys i got a 2001 2.2 sunfire automatic.. i know should of got manual tried but at the time mom had to drive it 2 times a week. i've heard these cars re very underrated and i figured since it a pretty light car maybe i can turn it into a sleeper. so heres a list of things i wuld like to get on the car and please add anything else you can get for my car on here to make it faster and have better handling. please do not tell me to sell the car im hell bent on keeping it only has 57,000 miles and never had any problems with it even since the original owner. also please dont be an *** only respond if your gonna try to help.

1. i would like to get a full exhaust system which im gnna get made at my local shop... but i was wonering what type of muffler i should get looking for more deep dont wanna sound like a crotch rocket.

2. header- i have only seen two brands for my car obx and pacesetter which is better?

3. already have a cold air intake but just a cheap one off ebay.. but ifound a brand called weapon r that makes one for my car are they any good?

this is all i got so far so please help help me out with the above questions and add more parts thanks for your help.