2009 PreRunner-2wd DC suspension

First, I apologize if this is a repeat question. Did some 'search' but couldn't find an exact(?) answer.
I recently bought an '09 PreRunner DC. Had the TSB for the suspension done on the leaf springs, including new bump stops. Could someone please tell me 1) the difference between the 2wd & 4wd suspension. I read ALOT about the 5100's. Are they just off-road shocks? 2) the TSB states that for the '09, "improved/upgraded" shocks have already been installed. I did notice that the shocks were NOT replaced at the time of the TSB. 3) What is the difference between the "old" shocks compared to the "improved" shocks?
Not having any problems with my truck, but would like to know a little more for future reference & upgrades.
Thanks for any imput from a new Taco owner & TW member.

 

There is no difference between the two, anything that fits the 4X4 suspension will fit a prerunner.

I've been through it all with my prerunner I'm running 5100 set at 0 with 885 springs and 1/2" top plate spacers, Light Racing UCA's and 2" AAL's.

 

There is a difference between the yellow/blue bilsteins and the 5100s. Mostly, the 5100 fronts have 4 positions for the spring perch which is where you get lift from. They can be set at 0, .85, 1.75 & 2.25 inches of lift. 1.5 or 2.0 AALs give you the lift out back.

 

Thanks. I also read the post by Toku58, reprinted by Khaos. Lots of good info & answered more of my questions.