Car troubles

Hey guys I'm not sure if this is the right thread to post this in, or if someone could direct me to the proper subreddit but I'm having a little bit of trouble diagnosing an electrical issue I'm having with my car.I drive a 1999 Seville w/ the bose sound system in it & in November I got an aftermarket head unit installed in it, no problem - no drainage. Then in January I got a sub & amp installed in the car as well and about a week after that I started having issues of my car dying. I took it to a mechanic and he told me that when the car is turned off, the speakers still pop. He did a test and my head unit is still drawing power while the car is turned off. It has been a minute since then but I believe he said it's drawing about 10/12's of a volt while the car is off. After that I started to "turn off" the head unit before exiting the car which improved battery life by about a day, but if I go more than a day without starting it, I'll come back to a dead vehicle. I then I took it back to my friend who originally installed both the head unit and the sub/amp and he said he couldn't find anything wrong with it as he checked for wire misplacements. I've tried disconnecting the sub from the battery as a solution before, but that did not end up helping at all. I was wondering if you guys had any solutions, ideas, or information that could help me find a solution to the problem. I'm unsure if this is necessary information but the type of head unit is a Pioneer AVH-X4800BS. Thanks for the help if you have any to give I really appreciate it via /r/cars http://ift.tt/2tbGUxD