What were the car attachments/retrofits in Looper?

Those are probably some kind of modified gasifiers which intake the exhaust fumes and convert them into consumable gas that would in turn run the engine. Gasification, was primarily done by burning fossil fuel like coal or wood. However, in my opinion the movie protrays some kind of an advanced gasifier that helps in fuel preservation, fuel re-cycling in a car and in turn run the engine with the outcome, more like a "Loop" (more appropriate if considered with the theme of the movie).