Ok, so I found another board I had laying around that has better PWM control than the Zotac and I've got what I think may be bad news. The mod doesn't work. It's entirely possible I may be screwing something up but, I'm pretty certain I did it right. The MoBo I used was a Foxconn 661GX7MJ-H which I downloaded the manual for, just to be on the safe side, so I could check it's CPU fan connector pinout. I "borrowed" a 4 pin PWM harness from a stock Intel cooler (who says they're useless? ) and soldered it on to the pump PCB making sure blue was on blue and green to the empty slot. I also switched the green and blue in the connector so that the blue was sense and green was control according to the MoBo manual. To make sure the PWM was actually working on the board, I used another stock Intel heat sink and artificially raised the temps (unplugged pump) and watched as both the CPU temp and fan RPM's go up to 50°C before plugging it back in. I tested this with both a 3.1 and a 3.25 and got the same results for both.

I really hope I did something wrong because it'd be a shame to have yet another version of the DDC running around to keep track of.

Someone please double check this.