Leepeen, before jumping into the whole aftermarket mod game, get some good synthetic oil in your Z. With stock oil I used to hit 240s easily. With high quality synthetics like Redline (which I have) or Motul, you'll get better engine protection. I can now only hit 220s (where I used to hit 240s easily with regular oil) with my current oil. If it still doesn't help, oil cooler is your only friend!
P.S. You must wait 3000 miles before switching to synthetic.