To my knowledge, most of the e36 cars have a factory amp. I would assume any of these cars that have the multiple speaker set up (1" tweets and 4" mids in door, 5.25 in the kick panel and 5.25 in the rear deck) would need an external factory amp to run all of that. I have never seen one of these cars without this speaker set up, so i guess they all do (have the factory amp). It is located under the rear seat. When i tapped the wire for the aftermarket amp turn on wire, i did so at the radio because i was replacing it and running rca's. if you don't wish to pull an amp turn on wire all the way from the radio location, i'm sure you could tap the factory amp location, but i dont know which lead terminating in the factory amp is the one that turns it on and off. I'll look into it or maybe someone will beat me to it and post the answer.