Pastrami is not just smoked corned beef. It has it's own unique rub and flavor profile. Sometimes a different seasoning in the cure also. And in a perfect world, it would be made with beef navel, but a lot of deli's use brisket. What I've learned over the years is that the rub should be primarily black pepper and coriander. There are other ingredients you can add, like garlic powder, onion powder, ground mustard, etc, but coriander should be the dominant flavor in order to taste like pastrami. Do not add pickling spices to the rub (like allspice, clove, ginger, cinnamon, mace, cardamom) or that little packet that comes with it, or it will end up tasting like smoked corned beef, which is not terrible, but it's not pastrami in my book. Plus, pastrami is always steamed after smoking in order to make it meltingly tender. My 2 cents. Everyone probably has their own idea of what pastrami should taste like. I try to mimic the best pastrami I've had in NY and in my local NY style deli, which don't have that "corned beef" flavor defined by pickling spices.