I found the culprit on my headset noise after installing my 796.
I have a music input jack, 1/8" little guy mounted on the gear tower since day one.
This jack is not isolated from the tower. As noted before, I wired the 796 audio to the back side of this jack, in parallel with the rest of the audio inputs for music. I never had any noise until installing the 796.
I have had to replace this jack a couple of times. Its not a very robust jack for the amount of use it gets. So after figuring out this was the culprit (unscrewed it while flying along and pushed it out of its mount, ignition noise went away immediately), I removed it and replaced with a 1/4" jack with isolators. This has cured my problem. Plus the 1/4" jack with a
90 deg adapter is a much more robust jack and should last a lot longer.