I can also rule out the ignition switch. After a lot of reading, I have found that the +12v start wire into the TFI module tells the distributor to ignore the spout - therefor reverting me to base timing. If the ignition switch was to go bad and be stuck 'on', I should be seeing a solid 10° timing, no matter what (@Boosted92LX ). That is not the case. I'm half tempted to try another distributor and see if that's the issue... again. It's not the MS, it's not the TFI, it's not the ignition switch.