Have you found a compressor map for the turbos you have? Compressor maps are not that difficult to understand and will tell you where in the efficiency range you fall. The T3 maps I have seen, which were for old T3's, looked like they were best suited to engines in the 1.8-2.2 size range, roughly, and that's based on the amount of boost you'd be doing with a little 4 banger. Even with 2 I think you will run out of capacity.