“Back Lash,” Chris Knopf’s new thriller, is nicely named because the protagonist-hero, Sam Acquillo, gets hit with a strong backward force that propels him into the past. Sam’s a cabinet maker in the Hamptons, but he used to be the head of an international research and development tech firm, and a professional boxer, whose winnings put him through MIT. Before that he was a kid living in the Bronx. Sam knows a lot about cars so another meaning of the title “Back Lash” applies — the jarring play