2013 Reg Cab 4x4 Leveling Kit? Add a leaf?

As the proud owner of a brand new 2013 single cab, manual, 4x4 tacoma I would like to raise the back end as it sags even with an empty bed.

My goal is to lift the rear end 2-3" affecting the ride quality, handling or gas mileage as little as possible. I would prefer it to sit level/ slightly nose down...

The tech at the dealership simply suggested an add a leaf for the rear only. If this is the way to go which one should I opt for?

Advice? Suggestions? Thoughts?

Thanks!

Dave