I had a simular deal with my MSD system on my Dart a while back.I have a billet dist ,6Al ,and a blaster 2 coil.It would start and run fine for a few minutes ,then it would begin to break up and then die,then wouldnt start back for awhile .It would then start and do it all over.After changing the coil ,cleaning my grounds and calling the MSD tech support , i could only figure the box was bad.When i would jumper wire the dist the box would churp like it should and fire ,then it wouldnt.I finally found the problem as i was taking the box off the car.It had a loose terminal on the hot side where it went to my starter.I ran it to the starter when i moved the battery to the trunk.The wire was making contact then it wouldnt.Thats box needs 12 full volts at all times...