How do restaurants make chicken fried rice? What ingredient am I missing?

Everytime I try to make chicken fried rice like I get at the take out place it never tastes like it does when they make it. We all know the basic ingredients

Rice (1 day old), Chicken, Green Onions, Sprouts, Eggs, Soy Sauce, MSG (optional)

I have a wok and I cook it just like them, I've heard all sorts of things as to what the "missing" or "secret" ingredient is. Some say it's a different type of soy sauce (not the standard La Choy) that they use.

I've been searching for definitive answers for this for a long time. It seems no one knows or anyone who's worked in a chinese place doesn't wish to share the knowledge. I went as far as adding MSG thinking that was what made the take-out place's Fried Rice taste different. MSG helps (sold as Accent Flavor Enhancer in your spice aisle) but that's not it.