A note on the NSX ring times. First, the 8:03.86 was run by a 1992 NA1 NSX-R in the Best Motoring Video Special Vol. 25. The driver was Motoharu Kurosawa and the track conditions were ideal, i.e., sunny and a completely dry track. The tire compund used is unknown, but the car appeared to be running on the OEM Type-R wheels and suspension.
Next, the 8:16.15 was run by a Formula Red European-spec LHD 1990 NSX coupe in the Best Motoring Video Special Vol. 15 (aka the "NSX Pass Around DVD" here on prime). Again, the driver was Kurosawa and the track conditions were ideal. It was running on OEM 15/16 wheels, but the tire compound is unknown.
Finally, I think Billy is on to something regarding the NA2 NSX-R time. That run comes from Video Special Vol. 55 and also features Kurosawa in ideal track conditions. However, if you watch the entire video, there is a quick cut to a shot of the garage before the run. On the floor are about a dozen sets of black springs and several wheels/tires. This suggests that the suspension was tuned specifically for the ring, with the stated goal of breaking the 8 minute mark. Also, at one time Vance had the Type-R suspension used in that run and he noted that it was not the same as the OEM Type R setup. Therefore, I think it is safe to say that the 7:56.73 time probably deserves an * for non-stock tires and non-stock suspension.
I think Jim's overall comment is very important. The Ring is a 20km circuit and can have extremely variable conditions. ALL of the above times were set in ideal track conditions. In addition, the driver can make a big difference on a course with more than 100 turns. Kurosawa is an experienced Ring driver and also is intimately familiar with the NSX. He knows how to squeeze every tenth out of that car and, if you watch the videos, he hangs it right out on the hairy edge to grab those times. The only other driver I have seen who drives that close to the edge of the NSX performance envelope is Senna. Magazine drivers like Motor Trend or Sport Auto might have guys that really know the Ring, but may not know the NSX as well. For example, these drivers may lift where a Kurosawa or Senna probably would keep the accelerator planted. Multiply that by 100 turns and you've got several seconds difference in times.
Another interesting consideration in the driver scenario is if you look at Kurosawa's times for other sports cars:
1989 R32 GT-R 8:22.38 (VIDEO SPECIAL VOL.6)
1991 911 turbo 8:08.73 (VIDEO SPECIAL VOL.21)
1995 R33 GT-R 8:01.72 (VIDEO SPECIAL VOL.32)
2004 WRX Sti SpecC 8:06.01 (2004 AUGUST ISSUE)
Given this range, the NSX times do not seem all that unreasonable to me. Maybe it is due to my being a lawyer, but I don't think you can make a case for the BM NSX times being doctored or fraudulent. Did they use some tweaks to get the new Type R under 8 minutes? Yeah, it seems like it. But, all that tinkering only seems to have bought them about 7 seconds faster than the NA1 R.
I agree. But it's still a good reference, and we need to be objective about the numbers. For the examples you gave, the 19 inch wheels may not do much, but the ceramic brakes will definitely cut a few seconds down. If you put the break in the consideration(weight, fading, etc) the numbers aren't far off. Like I mentioned about the NSX-R record, there are so many fine prints on the bottom that you need to read before judging/comparing the record.