I am running a 6AL box with blaster SS coil and MSD pro billet distributor on a big block (RB) Chrysler. In car for 5 years with coil being about 3 years old. Recently had car on chassis dyno and ignition dropped off at 3,700 rpm on all 4 pulls. HP and Torque lines were steadily increasing until 3,700 when they dropped momentarily and then picked back up again and were steady through end of pulls at 5,500. I can't be sure if this is new, or has been that way since I put the motor in 5 years ago. It's a street car and I rarely have the pedal to the floor in this RPM range. I did on the way home that day and did notice a momentary blip at that rpm. Motor is 10.5:1 comp, iron heads, new plugs, rotor and cap just before dyno pulls. I would suspect the coil or a ground problem except that it happened at the exact same RPM on each pull. Would appreciate any advice from anyone having had a solved a similar problem. Thank you in advance.