nope, no difference at all.
we all just like to give Dave more money when we buy impellers.
:biggrin:
I havent tested identical impellers back to back either. But if you do some searching, you will find that there are people who have, and they realised a difference.
that sort of thing is very hard to quantify, too many variables, water condition, and such.
My current is cut back 3mm, im tempted to send it in along with the pump and get it setback as far as it will go.. I will report the results when I do this.