OK so I have the AVIC Z130BT and just added a JL Audio HD900/5 amp, per JL Audio instructions and many youtube videos, I was convinced that I need to tune the amplifier per the suggested settings in the owners manual. I unhooked the speaker wires from the amp, turned everything off on the HU, bass, boost, loudness, etc. and set everything to flat on the EQ. Hooked up the DMM to the speaker ports on the amp, put in sine wave tone in cd to play at 1khz, turned up HU volume to 30 our 40 or 3/4 and proceeded to adjust the gain on the amp. Suggested setting on 4 ohm load is 20.0V, well problem,