Ok, I would keep v1.02 for now. The v1.03 isn't an official release so there maybe others forth coming, who knows. If you've done everything to load new FW and test in the same manor and seeing different results between each version then I presume something in the un-official version could be bad.
One thing you could test at some point, install a external Gb network switch between the router and all other wired devices to test. You'll be testing NICs and switch performance however this will eliminate any router processing interferences.