Originally Posted by Red__Zed

First off, there's a little bit of confusion going around about a lot of things, so I'm going to try to clear that up.

For the purpose of track discussion, stock-vs-stock is kind of pointless. First off, the Z can't run stock, so it is really not in it's favor to do that. Second, no one runs a completely stock car. Things like brakes, tires, and a reflash are a pretty safe bet, and I think allowing that and a oil cooler makes sense. So let's assume all the cars are running a lightweight set of rims that fit comfortably on the car in question-- something like the beefed up setup most of you are running on your Z's. Add track pads, etc, and give the cars a reflash. You're talking a very different game in this case from cars that are artificially limited by various things from the factory (less extreme version of the oil issues on the Z). You can uncork 30+AWHP with a $300 AP on a Subie, and the tire difference is huge too. The fact that the RE050a's grip better than SP's doesn't make the Z a better car. Part of the reason the Nismo tests so much better (besides just wider tires, etc) is the superior Advan's it comes with.

For the stock classing on autocross, you do need to understand there are a lot of other factors that come into play, like rules that benefit certain cars. Also, it's less important what a car runs in, but it is big deal when it gets moved. It means people are running the car, and failing-- and it usually means skilled people are giving it a go.
With the Z, the Nismo is basically allowed to run much fatter tires than anyone else, and in AutoX, that is huge. So Stock classing can give some misleading results-- from things like Nismos running 305s and WRXs running 245 series tires. That alone can be 5-6 seconds on most courses, and it's not really representative of the car's performance.

In regards to VIR, certain tracks benefit certain cars.
A car with good aero and a decent trap speed is usually going to dominate at VIR. At Here, the Nismo having an oil cooler is also going to be a huge benefit, since most cars are cooking it at the end of that straight--kind of an unfair benefit. Consider it offset by the fact that C&D maybe didn't get in a killer lap (though they claim they did).
It has always frustrated me that C&D uses VIR for their Lightning Lap...I wish they would pick a more balanced track. If they chose, say, Summit, the Subaru would probably be tearing things up--which is also not representative of performance. So quoting those numbers is pretty misleading. Allowing $500 to be spent on cars, (oil cooler for the Z, tune for mustang), a V6 mustang will put several seconds on the Z, and Jared will tell you that's not possible...