you should still be runing the standard maf and have the n75 unplugged, until its mapped.
Your vac reading at idel should still be the same weather you have changed turbo and other stuff. (I am only saying this from first hand experience from when I rebuilt my engine then changed turbo and Fmic)
I would take it some where to get it smoke tested to double check.that there is no leaks, leak could be anywhere. Under the manifold, pcv pipes, carbon canister pipes I think they are vacuum.
Just check every pipe lol it doesn't take up a massive amount of time.