There are more moving parts on a TT then a NA so there is more of a chance that a worn part could go bad, that being said if your Z is well taken care of you should not have any problems for both cars. I have had my Z new since 92' and I have had no major problems with my Z (It's has over 120,000 mile with original turbos) Also I recently dynoed 411 rhwp with my mod set up.
If Irememeber right when I was stock I was making 19-20 mpg. I don't know about the NA.