Sometimes noises are difficult to locate - even though you might be certain that it is coming from a specific area. While the TPS sounds like a good place to start you might want to check your drive shaft/line (maybe one of your CV joints have worn away). Often, when a CV joint has worn away you will experience moderate to heavy shaking of the car at various speeds. However, when you press the accelerator the problem seems to disappear.
Good luck!
