2005 Suzuki Swift Racing of engine while driving

When driving, in any gear, intermittently the engine will race, exceeding 3000rpm this continues even when the accelerator is no longer pressed. By putting the car in Neutral and applying the brakes is the only option to reduce speed as the car accelerates.
I have been tild it is some sirt if pipe that may have come off the engine. If this siunds familiar can somebody tell me which pipe and where it is located.
Thank you in advance.
Andy