I just wanted to know how much of a difference the 3.25 and 3.69 gears make in a cars performance. I would assume it helps with launches and such. I also wanted to know what a shift kit can do for a car.

You will get quicker accelration but lose top end HP. The shift kit will crisp up your shifts and lengthen the life of your clutches but may decrease the life of certain other parts of the tranny. Basically they shift faster allowing you to keep putting power to the ground with less lag between shifts. Also the PCM will pull timing during shifts to protect the tranny so the quicker the shift, the less the timing pull.

The higher gearing you have, the better launches and low speed runs you will have. However, you're top end will suffer.