Tom, welcome to the forum. You're one of many NY area transplants who have found there way here, looking for a taste of their youth.
You're probably not going to want to hear this, but, your cousin, if he opened his place in the last 15 years, most likely isn't producing a pizza of the caliber of your youth and thus probably isn't providing you with the knowledge you require. Since '82, almost every pizzeria in this area has taken a nose dive in quality and the new places that open just don't get it.
Ingredients are important, but, the most important factor in making great NY pizza is, by far, thermodynamics. Great NY pizza is defined by it's bake time. Faster heat transfer = greater oven spring/puffiness.
If your cousin is doing the typical 6-9 minute NY area bake, then he's making mediocre pizza. If you really want the taste of your youth, you should be aspiring for something greater.