What engine do you have?
if it the 3.0 check the compression before anything else.
3.4 or 3.0 check the MAF. every once in a while it and the intake from airfilter to manifold need a good cleaning with sensor safe electronics cleaner.
Use a soft old tooth brush with the cleaner on the tb and intake tubes, just spray the cleaner on the maf sensor, dont touch the sensor with anything, no fingers, toothbrushes, or cotton swabs as they may hurt it.