Watz up people, i have been hearing alot about these greddy turbos, are they any good? also, do they come in any twin kits?

 

Yes, they are amazingly great.
I don't think Greddy sells twin kits.
The T78 is greddys most popular turbocharger for RX-7s. Power potential is good... 400-500 rwhp @ 12-20 psi

 

Greddy makes a nice complete kit and they don't make twin kits. This is off topic but your name is almost the same as mine!!

 

Are there any other mods needed right away in order to run that t78 turbo? Also, around wat 1/4 mile times do you think that will give me?

 

Yes, it's not as easy as just slapping on the turbocharger.
Here is a rundown of the main things which need done:
- exhaust manifold
- ECU (preferably EMS)
- front mount intercooler and piping
- BOV and wastegate
- fuel injectors, pump, rails, lines
- ignition system
- full 3" - 3.5" exhaust system
- intake filter & piping
- clutch kit
- radiator
- oil cooler

It is also prefered to have your engine rebuilt and streetported before you put the turbocharger on. Your gains will be FAR more impresive with the streetport.
With a T78 on a streetported 13B, your power is dependent on the boost you run, but expect anywhere from 400-500 rwhp @ 15-25 psi.
It can put a stock weighing FD into the 11s or the 10s if you run higher boost.