How to downgrade my naff Iphone from ISO6 to ISO5.11 on a Mac?

I have tired to downgrade from ISO6 today as its too slow and maps is naff.
I have a mac and have tried the shift and click trick but it says no. It will not allow me to seach for a file on the mac and automagically gives me the ISO6 restore.

This is Apple you are talking about… No… No…