Well I think at this point, if I were you I'd try one more big pump. Any one of the normal Subaru ones- like walbro 416 an I'd run at least ten gauge power to it.
Then I'd get the maf into the fender and in a good spot and that should solve your problems.
Fwiw when I had my maf in the fender I originally used the ultimate racing maf housing. In short it sucked, the design and inside smoothness of it wasn't anything compared to the ks tech. Both looked the same at least close but they were worlds apart.