Blaster 2 coil stumbles

i installed a blaster 2 coil and my car now stumbles below 3K. what could be the problem? I put back in the stock one and the car is fine…
I tested the wires form the ignitor going to the new coil, the resistance is low. i also tested the wire form the coil to the distributor the resistance is also very low.

also how do u test the ignitor. I was looking through my chiltons and it doesnt really say how to test if it is working improperly. Just to test if it is broken