When a spark plug fires, it creates a great deal of radio frequency interference (RFI).  Uncontrolled, this can show up as static in the radio or other electronic devices, or more seriously, in electronic ignitions, fuel injection, and engine management systems.  This interference with EFI and engine management systems can cause "cross talk"  between wiring harnesses resulting in poor running, misfiring and decreased performance. Quality aftermarket spark plug wires suppress this interference resulting in consistent firing, smooth performance and possible fuel savings. Many companies make ignition wires to fit the Elantra. One of the best out there is available from Shark Racing. Their 8.5mm wires use custom made connectors and wires made by MSD.