I need some advice on my 99 4Runner rear suspension. It's got 119k miles now and I notice a lot of rear end sag when I put pretty much anything in the cargo area. I don't even have to be loaded down, it could just be 2 suitcases. If I am hauling 2 passengers, forget about it, it sags like a fat lady squatting down to pee!!
So, my question is, has anyone had this problem, and what did you do about it? People have told me that the 4Runners are notorious for this when they get older. I can purchase stock coil springs and shocks, but I feel the need to put on something better!! I'm currently thinking about new coil springs and Rancho RS9000XL shocks. I like the fact that these shocks are adjustable depending on what you're doing or hauling. Does anyone have any experience with these shocks? Pros/Cons? Thanks in advance for any guidance.

Your butt sag is normal when it has a few miles on it. For your truck check out Old Man Emu suspensions, it'll ride and handle better than new.

And I have the Rancho 90000s on my 84, and am totally unimpressed with them.

This is the perfect time to do a suspension lift.
If you don't want much lift, think about the Old Man Emu 906 coils for the back. OME 906 coils

I'm not a big fan of Ranchos.

Bilsteins are one of the best shocks, and my personal favorite.

I think the rear sag was way more prevalent in the 2nd gens, but these ones definitely will sag over time too. Remember that you're talking about springs that are over 15 years old.

And as for your specific question. Sorry, I have no feedback as I have no experience with those shocks.

I'm not sure how easily you can adjust them, but another option outside of those might be a set of airbags. Real easy to add a little help in the rear when you need.

your only choice is to put on an OME 3 inch lift... Check out fat bobs

My truck was sagging horribly when I purchased it. I quickly swapped out the old rear springs for land cruiser 9 wraps and bilstein shocks and I love them. For the fronts, I put on tundra bilstein shocks (5 spring perch settings) with my stock 99 springs. I have a slight rake to the front with this setup.
I tow my heavy ass wakeboard boat with it and the truck sits pretty level when towing.

My '99 had a saggy rear too. Like everyone else has said, change them out. That is what I did with OME 890s. Now it sits and rides a lot better and I have yet to see the rear of my '99 sag with the new coils (Loaded or Unloaded). Good luck!