Hi,
If you want to still go with 3.1, then I have a small fix for this issue
In 3.1, the S.open() method opens the url in the new tab (instead of new window).
Don't know the reason, but when it is loading in new tab, its becoming very slow.
So, I have changed the following file to force open the url in a new window (copied from 3.2 though!

)
Code:
funcunit/drivers/standard.js
in FuncUnit._open -> function
..
FuncUnit._window = window.open(url, "funcunit", "height=1000");
..
This may help you!
--
SuryaPavan