What ever happened to the slingshot?

What ever happened to the slingshot at plate races? I thought it was perfect for plate races so the winner isn't always relying on what 3rd place does (ex. Newman in the 500 w/ Kurt Busch). Does anyone know what happend to the aero package that ended it. Tony Stewart pulled a good one last year in the Nationwide car at Talladega but that has been it for a couple of years now.