CNG price in Mumbai as well as several other cities in the country has been hiked by Rs 2 per kg but users in poll-bound Delhi have been spared for the time being, according to city gas firms.Indraprastha Gas Ltd, the firm that retails CNG to automobiles and pipes natural gas to household kitchens for cooking in the national capital and adjoining cities, over the weekend raised CNG price by Rs 2 per kg.