Does anyone know if the signal coming out of the head unit is flat? I added an aftermarket sub, and first made a set of pig tails and T'd off the wires for the sub in the trunk...signal was clearly heavily rolled off/processed. I then ordered a harness made for GM vehicles with Bose, used one set of connectors and T'd off under the passenger seat, before the signal went into the Bose Amplifier, hoping the signal would be flat/clean there...to no avail. It still sounds rolled off/processed pre-bose amp. I'm wondering if anyone has tested the signal coming out of the head unit, prior to the Tuner Amp Unit, or does anyone know what the Tuner Amp Unit actually "does"? Meaning, is the TAU processing the head unit signal, or just acting as a junction box? At the end of the day, I'm trying to figure out if T'ing in prior to the TAU will have any "greater" effect in getting a flat/unprocessed/un-rolled off signal to carry back to my amp/sub. Other option I've read about is getting something like a Dayton DSP-408. Right now I have a frankenstein system with an old kenwood amp (no speaker level inputs), a Audiocontrol LC7i (leftover from another project, silly I know since I'm only using the sub channel) and JL 12w3. Everything's installed so swapping the LC7i for a DSP wouldn't be too terribly hard, I'd just rather make a T harness pre-TAU if it'll save me $100+ dollars. Thanks in advance if you've read this far, cheers!