Yes, installing larger valves will help a lot, even if the boss is still there, your turbo is forcing the A/F mixture in the combustion chambers. Your turbo will force the A/F mixture past the boss pretty easily.
You could just shave down/profile the boss smaller, just do not go too far where the head bolt goes through. With the turbo, shaving down the boss will help, just think of it as opening up a window, how much you can open up the window (making the boss smaller) will allow more airflow.
