[quote=mwaldrp;7195774]Do you mean spark plug wires? It's been at least 10 years since they were changed. Is there any way the alternator could be at fault? The volume change with rpm makes me suspicious.[/QUOTE
Spark increases/decreases with engine rpm. Wires much cheaper than an alternator. But it could be. If your wires are 10yrs old, how old are your plugs?