Too Lean??
 

All of my mods should be in my signature, i am thinking about getting a throttle body and plenum, would that make my care run too lean? I dont have any fuel mods and have almost every air mod there is, also I have a tuner but not sure how to do a custom tune to make it run more rich. Any help is greatly appreciated.

You should be fine. You will probably want to get a tune done just to add some fuel in certain areas but you will be fine.

so should i get a 75mm or 70mm for an NA stang?

dude i have the same issue i have a 03 GT i have stage 2 clutch, short thro, under drive pulleys, cold air intake, 75mm trick flow throttle body, 75mm trick flow upper plenum and a diablo pradator tuner and flowmaster exhaust im wondering if my injectors are holding me back to i think we are both ok im gunna just bump up my fuel a lil bit just to be safe untill i go get a air fuel meter

Both of you are fine. The factory tune will make the proper adjustments if you are running lean or rich. Just disconnect your battery when you install the TB/Plenum so that your computer can relearn the new fuel trims with your new found air.