Well it depends on how much money you want to spend. You can make a fake ram air by simply going to your hardware store, or you can buy a kit.
www.stangparts.com offers a kit, but I think it is kinda outrageous on price. The kit I have is the March ram air kit. It is supposed to add 15 horsepower when used along with their pulley's so total w/ pulleys 30 horsepower. I like the kit my stang has more torque and feels faster. One problem is the kit sucks up everything in its path, from leaves and snow to rocks. My only solution to that is to make a vaccume actuated door or simply mount a piece of plastic in it on a pieve of wire so tat it wobbles just like on the air induction on a funny car. Whn you hit the throttle it pulls air and opens the raim air, when you let off it closes??? Haven't tried that yet but am working on it........let me know in specific what you want to know about!!!