I initially thought that nothing could be made vegan here, and this belief was due to an employee at the location on Ina and Oracle telling me that nothing could be made vegan except for the white rice. Later, I researched online and found that there are items labeled vegetarian by a little green leaf. Vegetarianism excludes fish products, so I imagine this means that there is no fish sauce included in those dishes. This is again contrary to what I was initially told by an employee, but I can't imagine that corporate leaders of Pei Wei would not understand that vegetarians don't eat fish.
I have gone back to Pei Wei and have had the Spicy Korean dish with vegetables and tofu. The dish was excellent, though the last time I ordered it it tasted somewhat funky, like something was burnt or that the flavor of eggs transfered from something else they cooked before my dish. As with many restaurants, the cooks don't always clean their cooking apparatus, especially not when they are busy. I guess this is an issue I've come to accept, as I'm a student and need to often eat out as I can't always go home to cook.
I just found this website that lists what is vegan: