My L67 with your A2A kit on with the 19psi pulley only seeing 12-13psi max in the manifold. From my research it shouldn't loose that much psi but can't find any leaks.

Yes, you're right on that one. It should not lose that much. But, it mostly depends on how hot the outlet air temperature of the supercharger is and that how well does your A2A intercooler kit cools.