Changing the ring & pinion would provide a gearing advantage so having more power might not be necessary. The goal is better overall performance. You can get this my doing modifications to increase you horsepower and torque or you can reduce the load on your current engine. Smaller tires or improved gearing are both ways to do this but I am sure you don't want smaller tires.
My 4.88 ring & pinion with 35s are mathematically the gearing equivalent of stock tires and gearing. I the extra weight of the tires and rolling resistance clearly put me at a disadvantage compared to being stock, but if I still had 4.10 gearing I would expect it to take a significant increase in horsepower and torque (i.e. swap) to achieve similar performance results.
