Yes it does add a little bit of stiffness as the spacers pre-load the coil springs a little bit. Didn't bother me though. I've actually sold that truck since and picked up a X-Runner.
i know what your sayin. with the spacers it seems like the slightest bump in the road was doing damage. it was rough, and speed bumps were like HOLY CRAP!!I have the same lift on my Tacoma and I noticed that large bumps would feel very rough. I also have a TRD Off Road and it rode better stock than now. Do you have the same problem at all????