for a 92 legacy im pretty sure you wont need the error eliminator. i think people with the newer legacy's are getting them though (2003 +). About the Dual in Dual out harness.. Some cars need them and some dont. Its a relay harness that provides the lights with a larger amount of power/more stable power (power straight from the battery instead of the voltage from your original headlights) and it uses the 12v signal from your original headlights to activate the relays instead of powering the lights. The HIDs need to warm up, and they must have a certain voltage to "fire." It cant hurt to have the harness, but ide say if you were just ordering the 35 watt low beam HIDs dont get it. If you are going with Low and High beam HIDs ide say get the harness. Also if you go 55 watt, just to be safe i would get the harness since they use quite a bit more power and would place a significantly higher load on your factory wiring. 35 watts is enough for most people