ic... ok let say if i were to use 272 on the intake... thats means the duration of the opening should be longer rite?? em meaning that u can only select the duration of the cam(272,268,264,258, etc etc etc)... but u cant fine tune it with adjustable cam pulley, am i rite?? juts another question let say that u were to tune the exhaust side... i heard that by making the exhaust go out faster... it will benefits the engine in ways that.... it will create a vacuum to suck in more air from the intake.. also.... it will clear out any left over gases and make way for more fresh air for the next combustion cycle...