Measure out the arrowroot starch, tapioca flour, sweet rice flour, millet flour, whey protein, guar gum, xanthan gum and salt and put in the bowl of a stand mixer or a food processor (which is what I used).
In a large measuring cup, stir the eggs with the water and add to the dry ingredients. Mix on low until the dough starts to come together in chunks. Turn off the mixer and press the chunks together a couple of times to form a stiff dough.
Turn up the mixer speed and beat for two minutes. In the processor, the machine will start to labor when the dough is getting stiff, so take the dough out and knead it manually.
Divide the dough in 4-ounce portions, wrap the portions you are not using with plastic wrap, and either roll out with a rolling pin on the counter, or in a pasta making machine.
Make into sheets, then cut into noodles.
Cook the noodles in salted boiling water for 1 1/2 to 2 minutes, then test. They should be tender but firm, just a little softer than al dente dried pasta. Drain and rinse well with warm water if using warm, or cold if using cold, and serve immediately.