I have a pioneer GM-D8601. After hooking up, i turned the car to ACC and set the amp gains. Later when I turned the car all the way on to drive it out of my garage, the amp's power was way less. It sounded a lot quieter. I experimented and still can't find the issue. Occasionally with the car on I'll hear it come back in full power briefly. I've measured the power both at the battery and amp and I'm getting 12 volts with acc on and 14 volts with car on consistently with no voltage drops.
Help is very much appreciated.