This noise thing is a little weird to me. Are folks hearing the noise hearing two different types? I didn't notice any noises from normal use until checking after reading here. On my M Class if I hold it up to my ear when the screen is on I get a faint buzz/hum in either mode. No noise if the screen is off. When I fire it in TC mode, I get a louder rattle sound. (Only if held up to my ear.) No rattle sound when firing in power mode.
I have two other mods with Yihi chips in them. A Mini S Class & a Sig 100 (SX330 chip.) Both of them produce a fain buzz/hum when I hold them up to my ear when the screen is on. No rattle when firing.
The funny thing is that I never noticed a few things (like the sound) until it was posted here. Awhile ago someone posted about how the screen is slightly crooked to the frame. Mine is the same. Had my S Class for 5 months, decided to look closely at its screen, it is also slightly crooked. Never noticed before. Still the best two mods I ever used