I've used the Dali deflectors for years (no other ducting, just removed the shield) and am happy with them on the track. I use the big ones.
JeffA did a nice DIY writeup that shows how to do front AND rear ducts. With lots of photos. He's an Instructor and has tracked his NSX for years.
As for Porterfield's- my first track day in the Gallardo at VIR (new to me at the time) I had about 80% of the front pads remaining at the start of the day. This amount of pad would've lasted me at least 4 track days in the NSX. Granted the Gallardo is a faster and heavier car, but after six sessions (an admittedly long track day), the Porterfields were GONE. I was metal-to-metal and had to limp home, as I never dreamed that much pad could be toasted in one day. Disclaimer: I don't know what grade of Porterfield pads were on the car, as they were installed by the prior owner. Moral of the story: check your pads every few sessions no matter how much material you start with!!!!
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