Bring about 6 quarts of generously salted water (it should taste like the ocean) to a boil. Add the spaghetti Barilla and cook for 8 to 10 minutes or until al dente. When the pasta is done, reserve 1/2 cup of the water, then drain.
 

While the pasta is cooking, heat a large skillet over medium heat. Add the guanciale and sauté for about 3 minutes, or until the meat is crispy and golden and has rendered its fat. Turn off the heat. 
 

In a small bowl whisk the eggs and the cheeses until well-combined.
 

Return the guanciale pan to medium heat, and add half of the reserved pasta water to the pan. Toss in the spaghetti and agitate the pan over the heat for a few seconds until the bubbling subsides. Much of the water will evaporate

Remove the pan from the heat and add the egg mixture and stirring quickly until the eggs thicken. The residual heat will cook the eggs but work quickly to prevent the eggs from scrambling. If the sauce seems too thick, thin it out with a little bit more of the reserved pasta water.
 

Season liberally with freshly cracked black pepper. Taste for seasoning; depending on the kind of pork used, it may not need any salt.
 

Divide the pasta into bowls and serve immediately. You must eat this dish as soon as you make it.