I'm using a Q9550 E0 with my Rampage Formula, BIOS 0902. When I set FSB strap and FSB to 400 MHz, resulting in 3400 MHz for the CPU, I need 1.41 V MCH. Except in the last hot weeks, this setting runs stably, but NB temp was in the high 70s. But when I read your MCH temps, this seems to be quite high.

So maybe I should remove the chipset cooler and check for good contact?