Who's spark plug wires are everyone using? OEM? What aftermarket manufacturers?

 

What model/year? Generally I've used either Bougicord or OEM Volvo. I know FCP Euro sells both. Start by checking the date code on your existing wires to see how old they are then look for any corrosion under the boots. If the wires are over 5 years, time to replace. Also on some volvos (like the Gen 1 S40s) the wire harness to the coils can develop cracks in the connector insulation so if you are getting periodic misfires or runs rough on wet days, that may also be something to inspect.