hi i was wondering how much improvement i would get and the benifits of a lsd.
thanks

 

You do have an lsd.
All GTs have a traction lock diff which is Ford's version of limited slip.
It's not the best one in the world though so it's always good to upgrade it if you want more grip.

I didn't like the stock diff because it groaned a lot when making slow turns - probably needed to go back to the dealer for a fix but that wasn't happening....
I went with an Auburn. So far so good. I just finished breaking the gears in though so I haven't beat on it too much yet. It seems to grip really well though. Chirps the tires even when I'm not trying to.

 

if the one offered from brenspeed any good? i really want to get the best one i can since its 500+$

 

I really couldn't say if its the best... From the description on Brenspeed's site it sounds pretty good though. I guess it depends what you want to do with the car...
I thought about that one but decided on the Auburn because it was $400 and probably just as good...
If you are looking to put more power to the ground there are probably better upgrades. 1 piece driveshaft, etc...
I changed the diff mostly because of the noises it was making and I was changing the gears anyway... Also, a friend said he saw only 1 tire spinning when I was peeling out once. That alone was enough to make me want to upgrade.