Hi, I don't know that I can help much, but I'm curious about this also.

I got a '02 4Runner SR5 2wd with 77,000 miles about a month ago. It rides and handles surprisingly well! More car like.

My brother has an '01 with mileage close to yours and his rides a bit rougher.

We haven't had a lot of time, but have been trying to figure out what would be different.

Mine has no trailer hitch, so no "towing package." His has a hitch, but it looks to be after market and we're not sure yet if his shocks/springs are the same as mine.

He also has 16" rims and runs his pressures at 38psi. Mine are 15" and I run them at the factory recommended 29psi.

Btw, I have a new set of Goodrich Long Trail T/A tires. He has Michelin's, but I can't remember what model. I have to think sidewall stiffness might be part of the reason, plus his higher psi.

But, I realize there's more to it than tires. There is something going on with the suspension, I believe. So hopefully someone else will have some answers.

Thanks,
Ray K.