Just to let you guys know something. I had my wideband previously wired to the ground wire on my MS1 adapter cable. It still had a fair bit of noise, although much better than before. However the MTX-L resetting and failing to sync with the probe became a lot more frequent!
I unwired everything, but since I'm dyno testing my car tomorrow, I figured I'd wire the MTX-L back again temporarily. I wired it back like it was (+12V on IGN from radio and output 1 to the MS input)...
However, because I didn't want to take the protection plate from the footwell, I wired the ground to one of the plate retaining nuts. I figured I'd test it afterwards, and what do you know, the signal oscilations reduced even further!
So if wiring to 2A didn't solve it for you, I'd at least suggest you try this. It's effortless!
Attached are screenshots from the small log I took. You can see it only oscilates between 13.2 and 13.6 roughly, while standing still. The gauge was steady on 13.2 though.