"we are fast and you too" was denied, but is correct English. I have reported it. Imagine yourself standing there with a your friends saying this "we are fast", and you look at someone standing there, maybe on a different team, and say, "you too".
I politely disagree. Your example makes sense as a dialogue, but that sentence on its own sounds incomplete. On the other hand "We are fast and you are too" (notice the extra "are") makes perfect sense.