The basic requirements for a properly running engine are fuel, air, compression, and spark. Before increasing your engine's power, it's wise to ensure all maintenance is up-to-date and these processes are performing as intended. A weak spark from your ignition system can result in misfiring, rough idling, poor gas mileage, and damage to your catalytic converter, all of which hinder performance.Mishimoto ignition coils aim to provide high-quality replacements that can prepare your vehicle before moving on to improved horsepower and adding modifications. Our ignition coils are designed and tested to meet or exceed OEM Subaru performance standards. Once installed with a set of new spark plugs, one can expect a refreshed ignition system with improved engine startup, a smoother idle, and restored performance.----Mishimoto ignition coils are an ideal replacement for worn or defective factory coils. As with all our products, these ignition coils include our signature Mishimoto Lifetime Warranty.