By John S. McClenahen For the past several months, only a few economists have quietly questioned forecasts from the private economists and Federal Reserve projecting 4% real growth in U.S. GDP in 2004. That's starting to change, with some taking their doubts public. For example, David A. Rosenberg, chief North American economist at Merrill Lynch & Co., asks rhetorically, "Financial market conditions may indeed be stimulative, but where exactly is the pent-up demand to stimulate?" He sees growth at "little better" than 3% next year. "The most glaring imbalance is that as a nation, we have come out of recession overspent as opposed to underspent," he asserts.