I called MSD this week and ask them the same thing. got a new MSD coil cause my chrome Acell coil and chrome box got so hot I couldn't touch it. He said the MSD ss red plastic coil didn't need a resistor. even though the instructions said .8 ohm. so I left the .25 ohm one there.it got so hot I couldn't touch it either and quit. I think it burned out. so who knows what resistance is right.