You could play with the big brass screw on the top of the injector, jsut don't forget where you started with it. IT sounds like it mght be a bit rich and loading up, but in any case, try turning the big screw about the width of the slot first clockwise a few steps as you test it on each one If it gets worse, go the other way. Just don't forgot where you started, it doesn't take much of a turn to make a difference. You probably won't much past an eighth of a turn either way.
At least, that one is free and easy!
Bare