just an update to this thread:
1.) have not had to replace any of the original toilet components since the flow was reduced in 2009.
2.) One mistake I made was in not contacting the municipal water utility / engineering to see if they had any responsibility for the pressure of water supplied at the service entrance or any capacity to modify that. In retrospect, I should have done that first.
3.) fluid dynamics: http://sci301.uvi.edu/Plumbing/FluidDynamics.html