My ED is a slow POS! (Diff advice please)

[XRated]

Okay, I am tired of my car being a bloody slug. I need to get serious with diff gears, so I have a few questions I need answered before doing anything rash...

I want 3.9s.

What will my shitter rev at 110km/h?
Will my mid-top end be reduced?
Will my top speed be reduced?
I know against Commos for example at the moment, I pull away fairly easy past 100km/h, will I still have that advantage?
Is $1000 enough budget for LSD and new gears?

Thanks.