C5 Z06's were a tad lighter, and also had slightly shorter 1 - 3 gears. Not to mention, once you do major mods on a car.....they all react differently. Completely stock cars are going to be far more consistant than heavily modded cars that are all making similar horsepower.

It seems like Rick is making more power than he used to, and recently dyno'd with slightly higher horsepower, and substantially higher torque. Of course, dyno numbers don't really mean much since they are all different....but I'm willing to bet he's making 5 - 10 more rwhp, and 15+ more rwtq.