I will chime in on this front. I am not sure about the later Megasquirts, but in my experience V1 needed clean power, once we got to v2 (v2.2) the key was a good separate ground for the ecu and sensors, I would hope that later versions continue that trend. I have a trunk mounted battery and just bring a single feed forward to a distribution block, all engine electrics route from that single point, including the MS. No noise problems and I have over 10y on this system now.