Oil pan heater is now wired in with a quick disconnect plug.
I have since ridden the bike with the vacuum gauge sourcing vacuum from cylinders 1 and 4. Idle is hopeless, but once the bike is actually moving the needle steadies out and doesn't wiggle at all. The gauge is also mounted to the bike now, but its kind of ghetto and is hard to see unless I position myself correctly. As D.O.G. pointed out, there isn't much difference between full throttle and other throttle positions while accelerating. I can easily drop to 0.5 In Hg(?) or below when accelerating. When cruising however, the gauge does become useful, and the needle climbs up to around 4-8 In Hg(?). I believe off throttle was around 11. So far I have run two tanks through with the vacuum gauge installed, but I also adopted a new less accurate fillup technique to avoid fuel overflowing out of the cap when riding. Both fillups were at or above 60 MPG, so I have high hopes for this mod.