It's not been fudged, but it is not a real world performance test. It's a test on an engine dyno at full throttle with a different water pump, intake system, long tube headers, exhaust and often a different igntiion/computer system. If it's a magazine doing the test, they'll change the heads, intake and throttle body too on their "stock" engine!
More often than not, performance cams move the powerband higher and lose off the line torque and street manners but the tradeoff is high rpm full throttle performance. The cure is always to help get the engine into its new powerband quicker which is achieved by a higher stall converter and gears which often themselves reduce driveability.
If a track is not nearby, apps can be downloaded so speed tests can be run in Mexico, 0-60, 1/8-Mile, 1/4-Mile to measure gains or losses that way. I used to do both but drove around with a VC2000 on the dash as smart phones were still more than decade away.
These LS motors are a blast as I'm sure you can attest, they love to rev and have nice fat powerbands throughout their operating range, truly impressive. They adapt well to supercharging and turbocharging and make incredible power on boost.
If you do download one of those apps and find a lonely street, do let us know the numbers!
