Have I been doing this wrong all this time? I retard cams for high speed power and advance for low speed power.What's a few degrees between friends anyway? While factory timing figures are simply what the manufacturer found to work 'best' with the engine when new, much has changed including fuel, exhaust etc. .... so live and let live I say.
For what it's worth, by experimentation on many engines, I've always found that advancing the cam timing so that you've got no less than 0.030" piston to valve clearance works well with any cam profile for power at higher engine speeds while retarding the cam makes it pull well from low rpm. Just like ignition timing this is simply another tuning parameter rather than rigid dogma.
http://www.webcamshafts.com/index_blank.html?pages/cam_glossary.html