when you pull one waste gate vacuum line off, that means that turbo will have runaway boost up to 19- 20 psi on stock turbos. The other turbo will have boost up to the preset boost limit you have. So if one turbo does 20 psi and the other is set to like 12 psi , (20psi + 12psi) /2 = 16 psi because the manifold will equalize the pressure between the two. That 16 psi may be too much boost for your gasoline. The balance tube is doing it's job, balancing or averaging the boost between both sides. I am having too much fun bitch slapping you today.