Graphite tint is usually metallized, so that could be your problem.
I have no familiarity with stock sound systems; it's the first thing I get rid of when I buy a car. I suspect others here do the same, hence the lack of response here
You say there's no difference between dynamic on or off, what source are you using? Use tape or CD, not FM to determine this, as the signal strength/quality can impact your results. Since dynamic sound falls under signal processing, I would guess it's in the head unit, not the amplifier. E36 amps normally have built in crossovers, and that's pretty much the extent of signal processing they do. Like I said, I'm not too familiar, so I could be wrong here. The amp is located inside the driver's side rear side panel, if you wanna take a look at it. Hope this helps