2002 gtx di not running so hot!?!?

[9dakota7]

rocks sucked up and just had the wear ring and impellor replaced! ran great before the rocks and for an hr or so after the repairs, now doesnt keep at a steady speed and will shut off completely and throw you forward! the longer the key is out the longer u can go but the battery has been checked and is all good! everytime we go out after trying something else (battery test, spark plugs so far) it gets worse, any ideas? no maint lights coming on either if that helps! thanks