Get the computer scanned for trouble codes.Autozone and major parts chains all do this for free.See if any codes are stored.
Test the fuel pressure with a fuel pressure gauge,not just by pushing on the test port with a screwdriver...low fuel pressure could still be.
Another strong possibility is the IAC valve..sometimes these can be taken off and cleaned to correct this.May need replacement.
Check the Mass air flow sensor as well.
Just some thoughts