MSD pick-up polarity is something that MUST be checked. Several sources (including me) have reported finding a reverse polarity condition on brand new distributors right out of the box.
Another issue that we have seen at least a dozen times is the wiring from the box to the pick-up coil being reversed. In some cases, the wiring instructions right from MSD can be misleading.
With this quick change pigtail, the tuner can check for proper polarity in a few minutes or less.
MSD Test Pigtail for POLARITY of Pickup Coil
411-2323 - $16.50 USD