I have just noticed that I can see some sparking from the coil-to-distributor wire. It was actually arcing to the air intake if you can believe that. It would also arc to the cruise control throttle wire if it was close enough. I'm sure the wire must be bad (its original) but I wondered if there's anything else I should check when replacing it. The plug wires are only a couple years old. Have to wait a couple days before the wire is in anyway. Any input is much appreciated.

91 SR5 Xtra Cab, 298000km, 4" lift, 56" rear springs, 33-12.5R15 BFG Mud-Terran T/A KM2.....and an '85 axle still waiting to go in.