EW VISITORS TO FLUSHING might wonder if they've crossed several continents and landed in Asia when they emerge from the Main Street subway stop. The signs above bakeries, restaurants and newsstands along Main Street contain only Korean and Chinese characters. In the 1990s, immigrants from Taiwan and Korea began settling in Flushing, which now has the largest Korean-American community in New York City. With the boom has come rising prices and rents — a cause of friction between longtime residents and recent immigrants. But the spirit of religious freedom that motivated Flushing's residents in colonial times carries on in the community today.