I made a vegetarian carbonara the other night (with rigatoni) and it was probably the most difficult time I have ever had while cooking. I cursed it. But it tasted pretty good.
Miso works super good in vegan/vege pasta. A little white miso, mixed up with some water will mimic fatty/salty umami.
Also I couldn't work out what I wanted my partner to cook for my birthday, until reading this thread. She's makin carbonara - we even mail ordered guanciale and pecorino, and she'll handmake the pasta.
Hell yeah thanks everyone.