Originally Posted by GomangoCuda
Does the poly stiffen, slowdown or restrict movement? Would it be detrimental or advantageous for a strip or street/strip car?

Shouldn't matter. The shock should be controlling the damping.
If you're using 90/10 shocks, then maybe, but I doubt it.

The use is mostly for reducing compliance in cornering, or in the case of the strut rods, braking.