There are so many of these, that it's hard to get definitive answers. If I flash a dual processor 4,1 MacPro to the 5,1 firmware, then can I replace my 2.26Ghz E5520 processors with 3.2 Ghz W3670 processors? Is there any chance we could get a sticky going with which processors can work with each model of MP? I think it would save a lot of people a lot of trouble. Thanks!