Am I right or am I crazy?

[Jhunt94]

Not really sure where this post needs to go, but it pertains a little more to electrical I guess so I'll post it here. Pretty much ever since I installed my system, I've had a little more voltage drop that I thought I should have. When I initially installed everything, I didn't ground the amp to the frame, only to the body and I guessed that this might have had something to do with it. After putting it off forever I finally bought some wire and grounded it to the frame, and even though it helped a little bit, it still did not get rid of my problem. So then I started brainstorming and trying to figure out what else it could be, and decided that maybe I was sending a clipped signal through my amp and it was causing the bad voltage drop. I pulled out my handy dandy DD-1, but instead of using the Cd that came with it, I decided to use the tracks for the 3sixty.3 that you can find on Spotify because I've wondered if maybe the output was clipping at a different volume through the USB. When I was tuning it I did notice that clipping levels were a little different, and ever since then I've only been dropping like .3-.6 volts at full tilt.

What I'm pretty much asking is, was I right about what was causing the excessive voltage drop, was it just a coincidence, or what was it?