Since it's a 99 (my bad), with low miles, go with your basic 3.4 setup. Headers, Pulley, intake, and if you choose (It's recommended) a tune. You can get a canned tune from overkill, reptile or intense. Those are the good ones.

Also, plugs(autolite 104's, one heat range colder), wires, and 180* t stat.

Start there.