Daox, I'd be interested to see results in A-B-A form just for 5 minutes of driving the same route.... You may remember my (and Orange4boy's) problems with only running a single 12V battery actually reducing FE - sensors, injectors, computer normally running at 14.5V gave us trouble.
In my case I removed the serpentine belt, so removing alt, P/S, and a/c. Should have been a hefty benefit, but I actually experienced slightly lower FE over my repeated tests. My solution is on the way - a 4V battery to run my computer and injectors in series with my deep cycle. You'll see my thread on testing next week
Nice work with the wiring for the field wire kill - very clean job. (as always for you)