You might be able to gain a little bit with careful handloads using a slower powder like Blue Dot,but the 9mm just doesn’t have the case volume to do much with.
I tried to work up some 9 mm carbine loads. Don’t have the info handy but Blue Dot was way too slow, couldn’t get enough in the case to get decent velocity. With bullets heavier than 124 grain with I couldn’t get much improvement with any powder over a full sized pistol, just not enough space left in the case to work with.