You're in the wrong forum. Go here: Fox Engine Swaparoo - Mustang Forums at StangNet and ask away.
Your 84 is a fox (Ford's code for 79-93 Mustangs), aka a four-eye(4 headlights). Good luck. :nice:
First off I am partial to the 85 GT having owned one, and wouldn't change a thing. Yeah the 87 GT's were a hot car but the 85 is a classic. If you're curious about this car try this site: 1985 Mustang GT . Try restoring it to like-new condition before making any drastic changes. Done right...
Had an '01 with a squeak. Turned out to be a brake line in front of the rear wheels. The line passes through a metal loop and apparently wore though the coating on the brake line. Eventually it was metal on metal and squeaked like a mouse.
The "milk jug" circled isn't the air silencer. The air silencer is connected to the air filter box (below and to the left of the red circle) inside the fenderwell. IMO not worth the effort. You'll probably get more gain by waxing your car and reducing drag. :D
Sounds like you were still sleeping when you wrote this. The answer is no, you cannot change tunes by pressing a single button. The car needs to be turned off and the tuner needs to be connected to change tunes. There's no room on the computer to store an extra tune. Also O/D would not be...