Honestly, there is nothing wrong for a driver to drive a modded car, a Ferrari or whatever, as long as you drive within your limit and be responsibe.
The things is what you, as a 16 years old, will face in real world. are prejudgements from other people and extra comments/fingers pointing at you if you done anything wrong, such as accident, speeding or cutting off people lane. It's gonna be VERY VERY HARSH on you.
The other thing is, when other people see a 16 years old driving a modded import, exhaust noise and stuffs, they gonna thought you are a spoiled kid, cops gonna choose to stop you rather than a 40 yrs old driving the same Z, you will have to expect that's gonna happen alot, and you gonna hold your breath and stay calm.
Nobody will know you earn your own money to make this happen except us in this forum.
It sounds ridiculous and shallow, but sadly it is what it is.
Of course, we forum Z members always welcome any new Z owner.
It's just from looking at you background, 16 with 70k looking for a sport car with heavy mod in mind, it just makes us raise our eyebrows, but be expect it will happen to you in real world too.
Have fun on the buying, you might not need to mod it right away, an orginal Z is very very enjoyable to drive!!!
note: as long as you drive responsiblely, ppl gonna respect you.
cheers