You can search the forums for "amp adjustment" or "stereo sucks" or whatever, but in a nutshell, you can reach up inside the rear drivers side of the trunk, find a rectangular box in there, reach to the far end of it and twist a little flat knob to turn up the gain on the amp. It only drives the rear parcel shelf 7inch "subs", and it's only a 40w amp, so don't expect earth shattering results, but it does help a lot.