chbit63,
I am not sure what you are pumping, but here is my two pennies worth.
For Sewage Sludges TR185 (Frost) is used to calculate pipe friction losses when pumping viscous sludges.
In terms of correcting pump performance for viscosity with factors, each manufacturer's design de-rate differently, so a general programme will not be of much use.
When I need to de-rate centrifugals on viscous liquids, once I have selected the pump (in conjunction with the pump supplier), I ask them to give me a de-rated performance curve & if they are willing I ask them also for their de-ration info (factors , charts, graphs, etc) for future reference.
I hope this helps,
Berko