With that mileage I would check a few things;
Check the fuel pressure to make sure its within spec
Check the catalytic converter to make sure it has not collapsed in on itself and is blocking the exhaust.
Advance Auto or Auto Zone loans out test tool for the fuel pressure test. To check the converter you can bang on it with a mallet or hammer to listen for lose material. That does not mean it is not clogging the system though...just a check.
I am going to give you a diagnostic walk through for the general sistuation.
Tuesday, October 9th, 2012 AT 1:52 AM