Hello and welcome to Just answer.com, Super mechanic here. About your vehicle.
You will want to check the fuel pressure and make sure that it is not low.
Also, the fuel filter, that it's not clogged up or restricting the flow of fuel.
If they are both ok, then you might have a problem with the exhaust system being restricted. You can have an exhaust back pressure test done on it, or you can take out the 02 sensor that is closest to the engine, JUST AS A TEST and see if it runs much better. Thanks