Duration is what gives you a choppy idle. Duration is how long the valve is opened. You will notice choppy idles starting around 212 intake duration @ 0.50". More lift means more air and fuel into the cc. The LS6 cam is borderline from smooth to choppy. Its 207/217 .525 lift for the 01's but the 02's have slightly smaller intake duration but more lift. Something like this would be what you are lookin for. I mean hey they put these cams in 405hp motors. These cams in a 5.3 gives 50 hp increase on engine dyno.