Really it needs someone experienced to look at it and make sure everything is ok.

Although I guess that was largely the point of taking it to a tuner ? So what did they say about it ?

And if the boost control is plumbed exactly as AEM list in their instructions, there should be no difficulty making 16psi or more with very low controller duty.

Unless there is a major cam/tuning/turbo/tuning issue somewhere

Unless there are huge leaks, the intake and exhaust manifold certainly wont be the problem.

The larger turbine housing would be worth changing to a smaller one though as it should be relatively cheap.