I've got a problem with my rear end...need your help

I've got a problem with my rear end...need your advice

First, Happy New Year!

OK, not so-much a problem with MY rear-end, but the rear suspension of my '06 Titan CrewCab XE 2x4 >>>>with Tow Package<<<<<.

I bought this baby new, off the Nissan dealer's lot, in '06. It had everything I wanted except for the Tow Package. I didn't need it but the price was right and I was hot-n-bothered to get a new Titan.

I'm fed-up with the stiffness of the rear suspension. When I purchased the truck, I suspected the shocks had helper springs and I could just swap out the shocks. Wrong!

I keep about about 400 lbs. of bagged mulch in the bed as a temporary fix. Well, a year later, I'm ready to fix the problem.

Questions: Does the Tow Package version have an extra "layer" of leaf spring? If so, Is it possible to remove "it" or do I go with replacing the sets?

Is there another avenue to take to make the rear suspension not feel like a log wagon?

Thanks,
Bob