I'd recommend it..if your increasing power
Hi,
I lowered my 05 GT by 2" back and 1" front (Steeda Sport Springs). As I increased power by 50HP (underdrive pulley's and CAI) I felt a panhard brace was a good idea. This year I'm installing a Kenne-Bell blower with the intention of 430rwhp so any additional bracing is a good idea (I also installed trailing rear control arms as well to stiffen things up).
Cheers!