Yay, I'm glad that you are enjoying my quest, Norma! Although it's quite frustrating, a part of me finds it exhilerating.
In order to plan my dumpster diving excursion, I decided last night to look at my special pizzeria in Google Maps satellite image so that I could case the joint online. Well, as I zoomed in on the Google satellite image, I was shocked to see that the image showed a delivery truck parked at the back of the pizzeria! What amazing luck that this overhead image from a year or so ago just happened to have been taken when they were getting their food service delivery! The delivery truck shows a turquoise cab, so I quickly googled images of the Sysco food service trucks - no trucks with turquoise cabs. Then I googled FSA Foods trucks and, BINGO! FSA has the trucks with the turquoise cab! So now I definitively know that their cheese is Della Vita brand from FSA Foods.
So today I called FSA Foods to ask if it would be possible for a regular consumer to buy a loaf of their Della Vita Whole Milk Mozzarella. She said yes, they have a service where I can place an order, then come to the warehouse and pick it up. But it's $5 a pound, which is very expensive. I was so happy to find this out though and fully prepared to plunk down $30 for a loaf of their mozz. I got the Della Vita brochure off their website and it has all their Italian foods in it, like their canned tomatoes, cheeses, pre-made pizza crusts, pastas, etc. I might get some of those two so I can use all the same ingredients as my pizza place uses.
The thing is though: Today for the first time, I made a small pizza using the actual pizza sauce from my pizzeria that they gave me, and I used some old dough I had in the fridge plus my own mozz that I have on hand. Well, turns out my pizza had exactly the distinctive flavor of my pizza place, so I think their sauce IS the source of the flavor. Maybe I don't even need the Della Vita cheese they use, if the secret's in the sauce! I'll have to make another small pizza or two with their sauce to know with certainty if that's really the source of all the flavor, or if I need to spring for the expensive Della Vita Mozz.
I'm very happy that I am starting to 'crack the code.'
About the cheese, I think the grated cheese that I was given was quite white when they gave it to me, but then it yellowed with time because I had it at room temperature for a few hours, so it oxidized a bit.
I was thinking that to get their amazing flavor, they might be using MSG somewhere on their pizza, possibly. I may buy some Accent MSG seasoning at the store and try experimenting with it.
No, I never just get a cheese pizza because I love bell pepper and olives on my pizza, and at $20 per pizza I want it to taste as good as it can. Oh my goodness, it's so good. It's as if they plant little bombs in their sauce that are dormant when the sauce is cold, but explode and release amazing flavors when cooked. I'm really in awe of it.
Thanks for all of your invaluable advice and for being my sounding board!