Car runs and idles fine and even revs up fine. When driving seems to bog down on take off and wont get above 30mph with out bucking. When "floored" it makes clattering noises and not responsive. When I put my hand near the exhaust pipes and someone revs the engine up to 3000 rpm the exhuast exiting seems to go away. So low rpms you can feel exhaust fine, but when someone revs the engine it barely comes out. No typical CAT smell present, no hissing sound. What could this be?