I'm with Drach, LIM gaskets, and service the trans, ZZP's trans shift kit is a good product too, add an external trans cooler.

Decent mods to start with would be a 3.5 pulley, downpipe, highflow cat, (ubend delete) and an air intake with at least a pretuned PCM or dyno tune

Although at your mileage id consider changing the valve springs as a smaller pulley will probably cause the stock springs to float the valves enough to kill a decent amount of power