I've been tweaking my diet to be low-er carb (like 30g - 100g net carbs a day), but I can't really go high protein exactly (at least not while remaining vegan). I think for vegans/vegetarians, if you go low (or moderate?) carb, you automatically have to go higher fat... which isn't a bad thing. I did low carb before going vegetarian (now vegan), and even with lots lean protein it was very hard to go low fat.
Right now I eat a lot of soy protein, nuts (love PB2, defatted peanut butter), low carb veg and moderate carb veg.
I guess it's POSSIBLE to go vegan/really low carb/really high protein, but you'd also be super restricted in food options.