LANSING, Mich. – Many manufacturers and agribusinesses support a new trade deal with South Korea, one reason President Barack Obama and his counterpart from that nation are heading to suburban Detroit on Friday to tour a General Motors plant where cars are being built with South Korean parts. But the pact also will make it easier for South Korea to undercut some U.S. companies, leaving many workers leery of the deal — especially in economically struggling areas. The trade deal Congress passed Wednesday has the support of the United Auto Workers and the United Food and Commercial Workers. Both say it will create jobs in the U.S. by increasing auto and beef exports. Textile and steel workers say it will cost jobs, and even the U.S. International Trade Commission acknowledges the textile industry...