dude,

have u tried re-setting ur ECU if not already done so?

and is it throwing u any codes aswell? ..

Try cleaning ur O2 sensor on the exhaust.- To clean this just get a very light sand paper and rub it gently around the tip of the 02 sensor.

look around the engine bay and see if you have any vacume hoses that may be loose or is punctured. - replace if needed.

Also do u have or sense/hear any exhaust leaks?

as for what everyone else has said and you probably done/checked already,

try my remedy above and see how u go.