Lilpain....
You don't have an MPEM. It's the computer. Since yours is old... I would look at the Rev-limiter. They are known to go bad.
Alias123...
Unless there were other issues... I wouldn't have thought your MPEM was causing your problem. You have a 587 engine. If you lift the wire between the MPEM and the CDI... then it's either your stator coils, or the CDI. There are static tests outlined in the service manual to check the parts.