Wheelies: The Damage Control Edition January 17, 2012, 11:46 am Tesla Motors Chief Executive Elon Musk held a conference call on Tuesday morning to allay concerns that the departures of two executives indicated broader problems within the California-based company. Tesla announced last Friday that Peter Rawlinson, the company's vice president and chief engineer, left for undisclosed personal reasons. Mr. Musk said on Tuesday's call that Nick Sampson, a chassis engineering supervisor, was dismissed. After falling 19 percent on Friday afternoon, Tesla's stock was rebounding on Tuesday morning. The company still intends to sell its Model S sedan this summer and reveal a prototype of the Model X, Tesla's third vehicle, on Feb. 9, Mr. Musk said. General Motors announced Saturday that Tom Stephens, chief technology officer and a 43-year employee of the company, would retire effective April 1. Mr. Stephens led development of the Cadillac Northstar engines in the "90s and later worked on advanced propulsion projects, including those that led to the Chevrolet Volt. "Tom Stephens is an engineering icon within our company and within our industry," said Daniel F. Akerson, G.M. chairman and chief executive, in a statement. The British government has announced a new incentive program to encourage the adoption of plug-in delivery and passenger vans. The purchase of vans that meet emissions criteria will be subsidized by up to 20 percent of the van's price, up to a maximum £8,000, or about $12,000. To qualify, vans cannot expel more than 75 grams of carbon dioxide per kilometer and be capable of at least 60 miles of range between charges, or 10 miles in purely electric mode for plug-in hybrids. Society of Motor Manufacturers and Traders In an interview with the German business magazine WirtschaftsWoche, Matthias Müller, the Porsche chief executive, said the company's plans for a small midengine roadster to slot below the Boxster, which was refreshed for 2013, were on hold. "Possibly we need to wait until the next generation of customers before the idea of a small roadster will work for Porsche," he told the magazine. The model was to be co-developed with the Volkswagen Group subsidiaries Audi and Volkswagen. WirtschaftsWoche, via Car magazine