the blaster ss coil is .3 ohm , if you dont have a current limiting ign ( i think , and other ppl on here have said the stock 300e is) msd suggests an inline resistor

dont hold ur breath emailing msd tech, i still never got an answer from a month ago

worth noting, my tach works fine w MSD coil

PS mSD coils made in china, if i knew that i wldve prob gone w jacobs or something US made ...