The effusive Brooklyn Borough president Marty Markowitz just loves this focused tour. And who wouldn’t want to spend more than four hours downing a gut-busting range of insanely delicious slices, from the brick-oven Neapolitan style of Grimaldi’s to the authentic Sicilian squares of L&B Spumoni Gardens? A guide mouths off about the neighborhoods of Bay Ridge, Red Hook, Bensonhurst and more while you’re chewing.