Lawyer Maimon Kirschenbaum, the patron saint of underpaid waiters, has a new target. Kirschenbaum recently sued Heartland Brewery for shortchanging its part-time employees, and now he's filed a lawsuit alleging that busboys and waiters at four Upper West Side diners owned by Fanis Tsiamtsiouris — City Diner, Metro Diner, Key West Diner, and Manhattan Diner — were illegally paid a flat rate of $120 and $130 respectively (plus tips) for 60-hour workweeks (meaning they were paid about two bucks an hour). Joining busboy Raul Mendez in the class-action suit is chef Matthew Davis, who came to the diner after stints with Todd English and at Moomba and the Water Club. Davis tells us that over the next four years he was paid $100 less per week than he was originally promised; he says he was fired a day after the lawsuit was filed: “The owner said, ‘The place is not busy anymore.’” Tsiamtsiouris could not be reached for comment, but a 2004 New York article about diner economics hardly portrays him as a cheapskate: The man paid a decorator $40,000 to snazz up his City Diner.