Swore I posted again..

I'm 99% sure that my speaker whine issue is due to a ground loop (blown pico fuse in the headunit maybe?). All I know is the RCAs need to be grounded - so, I'll be visiting Jaycar tomorrow to buy some goodies to sort that out.

As for the engine bay whine, no idea. I thought my interior and engine bay whine were related (as they make the exact same sound) but unfortunately, that doesn't seem to be the case.