A group led by Minneapolis investor Irwin L. Jacobs said that it has raised its stake in Pittsburgh-based Allegheny International to 9.0% from 7.9% . . . The Daewoo Group of South Korea reported that it plans to add an auto assembly plant with an annual production capacity of 300,000 cars to its joint venture with General Motors . . . The board of San Diego-based Mail Boxes Etc., franchiser of postal and business service centers, has authorized the purchase of 100,000 shares or 4.6% of its common stock . . . Bethlehem Steel said it is boosting prices for carbon and alloy steel wire by about 4%, effective Oct. 1. It cited increases in the prices of steel scrap, aluminum and zinc . . . British Airways has purchased Bedford Associates, Jackson Heights, N.Y., a computer consultant firm specializing in the design, development and operation of high-performance systems, for an initial $8 million plus up to an additional $15 million payable over four years, depending upon performance.