Performance wise, theres not much out there but there are a few things you can do like remove the intake silencer, remove your 3rd cat and resonator and put on some highflow mufflers. I would stay away from bosch platinum plugs. I had bad luck with them as did some others but some didn't as you will see if you search. Don't go to far though because these transmissions (ax4n) are the weak link and our 275 hourses are already stretching their limits.
good luck with your findings.