Hey. Welcome to the forum! You'll get lots of good information here. There are functional ram air hoods for the 99+ Mustangs, unfortunately I am not sure if those kits work with the stock hood. I believe the ram air hoods have the scoops farther towards the front of the car, kinda looks like a nose. As for first mods: K&N filter, gears (you'll have to ask someone who has a GT but i think 3:73 or 4:10?), exhaust (cat-back, try to get stainless), or you can do what I did. Spent the money on the supercharger (cause I knew I would never do it if I didn't do it now
). Hope this helps a little!