[elisiX]

I think I got it.

I went behind the amp (literally the opposite side to the fins), and felt for the plug which was on the front of car end of what felt like another heat-sink on the back.

I couldn't see the plug, but it felt like what you show in image 2. I'm sure I disabled the right cable - it's on the back (outside wall) of the rear 1/4.

After going for a drive however, the sound I have been describing is still there. It did seem like the cabin was quieter, which I assume is ASD being disabled.

However the artificial electronic sound is still there. It's very obvious when coming off the throttle and the engine is revving down.

Really lost at this point.