With regards to the timing,advancing or retarding will have an effect on the power curve,max advance will make the engine responsive and snappy where as retarding the timing from here will give less response but more revs before dropping off power,known as overrev,so you can hang on to a gear between corners without having to shut off or shift up.
Regarding the cam timing,if someones spent money buying a performance cam,obviously they want it to work as it should.If its not set to whats recommended by the cam manufacture,you will be losing the performance you paid for.
An engine can perform OK with it being out,but this is only a perception that its running fine.
Without setting it properly you will never know how its supposed to perform.
Its a pain,yes,but its a waste of money if you just leave it.
dave
Edited by Dave33, 24 June 2010 - 11:17 AM.