Coil mounting

I have an MSD Blaster SS E-core coil mounted on the firewall next to the distributor. I orignally had a Blaster 2 mounted in the stock location but it started acting up after a couple of years and that is when I learned MSD recomends that there oil filled coils not be mounted horizontally. Don't know if that is why it went bad or not but if you have a Blaster 2 coil I would follow there recomendations.