Feel free to ignore if you don't use or own a Moka.
Oh, yes, I forgot to share this tidbit. As I said, I recently changed the gaskets on the mokas I own. The ones from rubber to silicone. I saw an improvement in "shots." However, I still faced bubbling issues. I woke up early this morning and started testing out on four different mokas I had in the 6 cup range. A starting preheat temp of around 90-102* F or 32-39* C (rounded), yields a very even stream from start to finish between medium and low flame. This is obviously dependent on how your burner settings are presuming you use a gas stovetop. You may have to take the knobs off and use a tool to fiddle with the gas regulator screw. Only at the very last few teaspoons did the moka sputter. I went ahead and repeated the test a few times.
This confirmed my findings and because I addressed the issue of a lighter/blonde brew coming up then turning into that black, gorgeous silkiness. In the lighter/blonde issues, I suspected it was remaining water I didn't quite dry out in the main chamber after giving it a once over with fresh water. Stainless steel mokas are designed differently than the traditional ones. I later discovered I wasn't packing in the grounds very well which lead to multiple channels opening up before the puck became pressed against the top filter and the brew darkened.
Brewing from 90-102* F allowed some oxygen in the water (though if you use mineral water, the taste is even better) before boiling inside, whereas off boiled water has little to no oxygen. Chemistry isn't my forte, but I suspect it makes a difference during contact time with the grounds. AFAIK from what I've read and seen in person, Italians typically use room temperature water or slightly chilled water. I've come pretty close to what I've had made by the hands of a native.
As an aside, may I suggest anyone who uses a moka to drop a nice shaving of orange peel in the main section as the brew is about to come down. It's delightful. Just remember to avoid dairy unless you enjoy curds in your coffee.
ETA: I dumped about 2 kilos worth of used pucks and grounds into the rose bushes yesterday evening, then turned some of the soil over with a small shovel. I don't feel comfortable using the regular bonemeal and worm castings I use with the kids walking around everywhere now. The company claims to UV sanitize it, but better safe than sorry. I'll switch to fish kelp in the winter, since there's no odor then.
I'm currently testing out some new mixtures for my used pucks. Mixtures for starting wood fires. Aiming for a cleaner burn unlike the current mixtures people use.