Mark & Andrew,
I do not have a ballast resistor in the system. I run a MSD6AL and Blaster 2 coil-these have been on the car for years. When I checked the sense line voltage at the VR, I removed the VR plug, positive side of the meter directly into the plug female connector and negative side of the meter to the VR bolt that also holds the ground strap to the engine. The VR plug connects quite tightly to the VR terminals-it requires some effort to remove the plug.
might not make a difference, but don't use the bolt head for ground. use the vr case body. just in case.
then see if it is different if you use battery ground.
again, last test would be to run a pos line direct from the battery to the feed to the vr. I think you might be able to tap into the msd feed, but not familar enough with that wiring. That is to say without cutting and splicing into a line.
