I think I have a MSD problem!?

Here's what I got guys. Drove to a show and noticed that the tach would jump at times( about a couple hundred rpm's). Not to bad at first, then more so. Now it misses at higher rpm's under a load. It will idle and rev up all day with no load on it.
what do you guys think? The MSD box was built in 1999. So maybe it is starting to take a dump? It's a 6al box. Anybody ever have this problem?