unless you're going for more than 600 RWHP, and then you'll want to go with 3" piping. Although I wasn't a fan of the quad 4" ovals, the one I just shipped looked awesome (2 1/2" piping) and I'm considering that same exhaust for my Z. The difference in the tips is simply personal preference and will not affect your power. If you do want an exhaust in 3 weeks, you should know that B&B doesn't make an exhaust until it is ordered, and then they make exactly the way that you order it. Normal time is 2 weeks (I was told) but the last one took over 3 to be fabricated.