If your use "group by" in your select statements, it works different in VFP 9.
There may be other items but this is the one I remember.
After I converted them, I learned you could set compatibility to solve the probem without changing code.
You would have to look that one up.

I can not address the speed issue there are too many variables.
I have no speed issues with VFP 9.

Will wc 4.66 work with Foxpro 9? I am thinking of upgrading VFP 6 to VFP 9 and am wondering will all my code work, and if so will it work faster?