Christ you guys can be unhelpful at times.
Serious response: The throttle on the Z is "smoothed" in gears 1 to 3, taking an old school wire throttle and replacing it with an elastic band is roughly how Mark@Abbey described it to me, i.e: you put you foot fully down and the car slowly moves to 100% rather than an immediate 100% throttle. I'm guessing you don't realise so much in 1st & 2nd as you don't tend to cruise around in those gears. If you'r after more responsiveness get an uprev - although you may want to consider a few other changes before hand. On the flip side, if you do a lot of city driving the extra responsiveness can be a negative as the "smoothed" throttle can help in stop/start traffic.
Speak to Abbey, RS Tuning or Horsham (all 3 on here) and they will give good advice on how to get the car where you want it - the 350Z is a lovely car in terms of being able to match it to the owners style.