I took my car to get Dyno yesterday here are the results for a 02 Z28 B4C 6-speed with these Mods:
1.Ram Air box SLP
2.K&N
3.Mass Air SLP
4.Flowmaster 80
5.Mobile one<if anyone cares>

1. First run MAX POWER=298.4 Max TORQUE =319.2
2. Sen run MAX POWER=297.8 MAX TORQUE= 317.8
Now I had read that true HP was based more on torque but I'm still happy with these numbers considering this car was rated @ 305 @ the motor so it more like 340/345 @ the motor. But I always thought the car pulled really well. Now my friends 03 cobra was dyno @ 370/330torque.

 

Good numbers, but remember that the dealer way underates these cars. So, its nothing amazing that you have 345 at the motor. A typical LS1 dynoes between 290-320 at the wheels.

 

i think GM not the Dealer is the one that underrates them.. but I think, as most others, that the motors HP is not as high as others feel it is.. mainly because the parasitic drag isnt as large of a percentage as others claim it is.. I do think 15% would be the max loss..
JMO tho...