runs like a vac leak

Had something similar happen once, and it was a bad seal between carb and intake. It is worth checking. Also, and I am almost embarrassed to suggest it, make sure there are no unplugged 'holes' in the carb. It is within the realm of possibility that a new out-of-the-box carb could have been installed with a vacuum port open that needs to be plugged. I've seen it happen.