Well all new cars come with cats! you have to tell them what gears you have and wether your car is manual or auto! underneath your car in the idle of both wheels you will see the pumpkin and a sticker reading your gear ratio! I suspect it will say 3.31 since its stock I believe! as for what size maf housing comes with you steeda, I would go to their site n check it out1 prolly 90mm cuz 80 i stock(i think) and that cai requires a tune. But yeah that info is a must as well as ur pcm code...
2010 gt premium
Steeda strut tower brace
C&l n CR/AM Tune coming soon
18'' bullitt style wheels
selling '10 v6 stock wheels and Gt mufflers