Glad to see another "ex-pat" New Yorker
Greenwich Village guy here. I, too, have been in perennial search for the perfect NY pizza recipe. Here's what I've learned (some of which has already been covered):
--High-gluten flour is a must.
--Use a pizza stone (or unglazed quarry tiles) on the lowest rack of the oven, and get the oven up to highest temp possible (as Steve pointed out).
--I really like the 6-in-1, but have yet to come up with a great "NY sauce" recipe, because I just found a place that sells the 6-in-1 locally. If I find anything out I'll pass it along. Mind you, I also haven't tried Redpack brand yet either, but I can't see it being much better than the 6-in-1.
--I hate to disagree with Steve on this, since he's right about just about everything else, but it's okay to do the whole-milk cheese thing on the pizza if you're trying for a NYC pizza. I've used whole-milk cheese with excellent results. Not that the other cheeses he mentioned wouldn't work as well--they will.
--I would say the 24-hour refrigeration of the dough is a must for taste and handling purposes. Closed plastic bag is fine.
--What kind of NY pizza exactly are you looking to emulate? The normal "street pizzeria" kind, or the "elite" brick-oven, old-school kind of Lombardi's, Grimaldi's, Patsy's, and the like?