The recovery in American auto sales from the lowest levels in almost three decades may spur a wave of  acquisitions of auto-parts makers by hedge funds, private equity firms and rival manufacturers after a two-year slump, Bloomberg News reports.Johnson Controls’s $1.25 billion offer for the bankrupt Visteon Corporation, announced May 21, is the largest by a parts maker this year, according to data compiled by Bloomberg. BorgWarner and Federal-Mogul say they are seeking acquisitions, and Wilbur Ross’s WL Ross & Co. says the takeover environment is improving.