1st gear is still useful and the car pulls so much harder in all gears. I lost a couple mpg's on the highway, but around town is about the same as factory gearing (3.73 in my car originally). At the drag strip, the 4.56's dropped my 60' times by 3 tenths of a second!

 

Yeah i loved my 4.10s in my 04 gt, just hated the drone associated with gears and no cats. Think I'll stick with 3.73s and cats on my 13', just less headache.

 

I have a base GT with 3.73s, but I have the track package.