The mid 1980s were the beginning of the end for distributors in regard to new cars. The Buick grand nationals started using coil pack technology while many other GM vehicles were using dual tower coil packs sometimes known as waste spark systems. Others followed. Other common applications came from Mitsubishi and eventually Chrysler systems. MSD's DIS ignition controls are designed for engines with coil pack, waste spark ignition systems. The DIS-2 has two channels, to fire two coil packs, while the DIS-4 is capable of firing up to four coil packs, even 4 individual coils. Each control delivers full power capacitive discharge sparks from idle through racing RPM. Below 3, 00 RPM there is a series of multiple sparks that last for up to 20 degrees of crank shaft rotation to improve idle, starting and throttle response. These also come with many adjustable features through rotary dials. Includes over rev and hole shot protection, plus a step retard.