MSD 6AL Issues

[sixtnine]

Any input from you guys would be great! I have developed a miss under load. I can free rev the engine with no miss. My ignition combo is a MSD 85551 dist., blaster SS coil, and 6AL box. I have ruled out the dist. and plugs. In my past experience the ignition boxes work or do not work. The coil and box are hidden underneath the dash. The 6AL has developed a louder than normal buzzing noise lately. I spoke with MSD tech and they said the noise could be from the deterioration of silicone used inside on some parts, but it would not effect the box working. Before I replace everything does anyone have any suggestions. I have a lot of friends who wrench for a living and we are all kinda baffled over the miss. Thanks again for any input.