Our's do not humm or whine... Although the 5 color one's almost scream while operating. (I never recommend those to any of my customers.) The transformers we have are in a plastic casing completelt sealed with epoxy... There is no air or anything getting into the transformer box. I can take a pic and show you this design.
BTW - I could've done the same thing as you... Wiped the faces of the Saturn indiglo gauges clean (which happen to be exactly the same size as ours (99+)... and overlayed our graphics.. (and done it for about $10.00 cheaper than you did) but that's not quality nor what I would prefer in my dash.
Glad to see your outlook turned a bit.
Doc
