Our Firecore mech and our CD Coil. I can honestly say that the timing is rock-steady with the timing light. Took it to 6 grand, dead-nuts 35 degrees. Never moved. Can't wait to race it. I could spin the distributor 180 degrees if I wanted to. Those who are on the fence, you will not be disappointed. The MSD's are selling used for the same price a new FC Mechanical is selling for..