This is absolutely not correct... PST's stuff is graphite impregnated polyurethane, thus the name polygraphite. They claim the graphite functions to eliminate the usual squeaking of polyurethane, which it does seem to do.
I installed PST's polygraphite front
suspension kit on my Mach in 1990, and proceeded to drive the car daily until '94ish, putting over 30k miles on it during that time. And recently when restoring the car, I was going to rebuild the
suspension with PST's kit again. But when we pulled the
suspension apart, none of the old PST stuff needed to be replaced. Everything was still in really good shape, with very minimal wear. We ended up using all of it again.
Overall, the PST bushings were probably made the biggest difference in the handling of the car and feel tight and firm. I recommend it.