Running the right plugs, Champion Cooper with a gap of .50
Decent wire set.
Clean upper intake specially around the egr area.
Replace the trunk size muffler under neath something better flowing/smaller. (Added bonus weight savings)
I run 10w30 Mobil oil with a K&N oil filter. Good Oil is a must for longevity.
Far as performance, putting a 58mm TB on (stock is 52mm) is the easiest/biggest thing you can do. Porting/gasket matching the upper and lower intake also can be done.
Exhuast once again. Stock muffler not the greatest.
Non ethanol fuel would help the best in regaining lost MPGs.
That's about it for easy stuff.