Pull the fuse on those aftermarket wires and see what stops working. If you can't figure it out pull that po butcher job right out. I remember when I got mine it must have had 3 head units in the console over the years. Each installer hacked something else up to install their head unit and by the time I got the car there were so many wires behind the radio it wouldn't slide back!
So my dad and I spent and afternoon tracking them down and cutting it out. We removed and amazing amount of wire, one guy took power for the radio off the fader switch, the other was off the old car phone harness. In the end we found the original MB wires for the radio intact so we took power off them for my new headunit.
Also replace all the fuses with the updated copper ones.