I agree with Kat, and also WelshStump. Some dogs can't tolerate pork. Some are fine, but I know my dog, when I feed her pork, gets really bad gas (sorry, TMI!) which seems to be indicative of a less-than-happy stomach. I don't feed pork for that reason. You might try a different meat and see if that helps. Kat has good advice, though!
Edited to add: The throwing up seems like an indicator of a bigger problem, to me. Not sure what would cause it, but I would talk to your vet. Might not be the food necesarily, but some other stomach issue.