I have the 4" springs all around on my 1990. The rear works good if I have a lot of wieght in the back. I have the stock bed and with out my gear its stiff and doesn't flex to good. I carry a lot of crap when I go( spare parts,tools,camping stuff, etc..) so the add pounds make those springs work. You might try pulling out the bottum leaf and the next one up. These springs have a 250LB spring rate and they should have a 125-175lb( if on a pickup). There designed to work on the all 79-95 trucks which includes the heavier 90-95 4runners.
