No, you can get one without a chip and use it.
Most combos run better a little leaner. It may only lean it out on the top end (wide open throttle..see above) because you are in open loop (not using feedback info from the sensors to adjust fuel pressure...again, see above explanation) but that is still beneficial to you and can make your car perform better. Try 39 psi, then 37 psi, down to 35 for the best results, but dont go any lower than that.
------------------
1993 GT/AOD
'93 Mustang GT