Reuters: Luxury carmaker Porsche said on Tuesday it planned to legally challenge London mayor Ken Livingstone’s decision to help fight global warming by taxing gas guzzling cars driving in the city centre. Porsche said on Tuesday the 25 pound ($48.74) daily charge was unfair, would not cut emissions of carbon dioxide and would deter businesses from moving to the city. "A massive congestion charge increase is quite simply unjust," said Andy Goss, Managing Director of Porsche Cars GB. …