Why are some coils side specific and some not?? I know the stock springs are

 

Personally, I think the better quality springs are going to be side specific. My NWOR Springs are. OME Prado Springs are, but according them, the 4Runner isn't heavy enough to warrant different springs for the left/right weight issue. Plus, the Prado that's sold in Australia is Right Hand Drive, adding to the side-specific weight offset.

If you install SAW Coil-Overs, you will need to crank the Driver's side a tad more than the Pasenger side to achieve equal lift. I have read a few things about the PP's not giving equal lift up front and you end up with the Passenger side being higher than the Driver's.

My .02
Dr. Z