Yeah, hate to say it.... but I don't know how much more you can do.
I think you need to find a happy medium when dealing with these behaviours. As in; don't ignore it outright, that sends the message that it's ok. But don't lose your mind over it either, or you will feel like all day long you are yelling NO- NO -NO- NO- NO -NO. LoL
When they are acting up, use your firm daycare-lady voice and remind them what you expect. "We do NOT growl at our friends, we use our words." Definitely don't respond to the grunting and shrieking. They are old enough to understand what you are saying, when you ask them to use their words.
As for screaming; I HATE that phase. Really what can you do, other than sequestering them so we can't hear it anymore??? I found that if they are doing it at the table, turning their seat around so that they can't see each other works on occasion.
I would absolutely continue with time outs, etc for hitting/ pushing and so on. Aggression towards others is one thing that I begin to give consequences for at a very young age. Under no circumstances is it ok to try to hurt our friends.
Having kids all the same age can be great, but this is definitely one of the downsides. They all seem to play off each other somedays, and bring out the worst!!