My Bonneville 'rumbles' between 40 and 50 mph. I think it'* related to the spark plug wires; when I went to the store and bought spark plug wires (Xact) there were 5 in the box. When I looked under the hood, there are 6 wires. Is there any specific brand I need to buy? Thanks.

You're missing one in the box. 6 cylinders = 6 wires.

The buzz around here for wires is the lifetime warranty Belden wires available at Napa. Mine were about $38.

Oke-doke, I'll try Belden; the picture on the box showed 5 wires, too, so I was a little surprised. Thanks randman.