Will just changing the axle back system make a noticable difference in the sound or would you also need headers and mid-pipe?

 

Ya depending on which brand you go with.

 

Absolutely, axle backsby themselvescan provide an INCREDIBLE increase in gorgeous, hearty, throaty, american muscle sound! Check out the forum's exhaust thread for a lot of info and sound clips of many variations. Best bet is to find a Stang club near you and listen for yourself.

 

axle backs are a good place to start
if thats not enough you can add LT's and mid pipe later, the LT's and o/r x pipe made my exhaust 10x louder than just the axlebacks alone.
nothing wrong w/ changing your exhaust more than once, i know i changed mine 3x already, and i'll probly change it again sooner or later