In a large bowl, combine the flours and nutritional yeast.
Put everything else (except the broth) into a food processor and combine.
Mix the spices into the dry ingredients and add the 1 1/4 cus of broth to mix everything together. If it's too wet, add more gluten, if it's too dry, add more broth.When it's all combined, make it into a loaf-shape and wrap with cheesecloth to keep it that way. Place into a slow cooker and cover with the remaining 6 cups of broth. Cook on low for 8 hours. Let it cool in the broth.
Tzatziki
Mix everything together. Let it rest.
Gyros
Slice the seitan into meatly shapes and cook in a grill pan over medium until it's crispy on the edges. Spritz with Bragg's Aminos for color and salt.
Heat the pitas in a toaster oven or on the stovetop. Assemble with seitan first, sauce, onions, tomatoes. Serve with extra napkins.