the cobra in question...the "lawsuit cobra" was the 99 model. they advertised 320hp, but were proven to only make 305. it took a computer upgrade, different intake manifold, and exhaust system in a recall to make the advertised power.
as for the LS1 cars, that was al dumb from the get-go on GMs part. it was the exact same engine in the corvette and the f-bodies, but the camaro and firebird mysteriously had less power? that was just GM trying to keep the vette owners feeling superior to the f-body owners...