Business is good for the Indy Racing Experience, which was founded in a Gasoline Alley shop in 1987. The company, which started allowing fans to ride around the Indianapolis Motor Speedway in two-seat open-wheel cars in 2000, quietly began letting fans drive a real Indy race car last year. This year, company officials said, driving slots for the Experience in May are sold out and business is up more than 100 percent from last year