here is another view on the subject of advancing or retarding a cam. Some of the latest books on the subect consider it "nonsense" and here is why.
Desktop Dynos : Using Computers to Build and Test Engines
Page 92
If advancing or retarding the cam is such a "poor practice" why is it so popular? The answer is simple: It is just about the only "tuning" change available to the engine builder without regrinding or replacing the cam. Advancing the cam slightly improves low-speed power, while retarding the cam gives a small boost in high speed power. If advancing or retarding allows the engine to perform better, the cam profile was not optimum in the first place.
hope this info was interesting
Andy