The cam changes the sound of your exhaust because it changes when and for how long the valves open, as well as lifts them higher. The rockers just increase the valve lift.
As far as ZZP's charts go: They're just a guide and not a rule. 1.9 rockers will allow you to run about the same size pulley as a VS cam. So, the answer to that question is both yes and no. Yes, you can run a 3.3 non-intercooled with a set of rockers and other supporting mods (this would be like having a VS cam instead of the 1.9 rockers). No, you cannot run a 3.1 with rockers and no type of intercooler, like you could with an XP cam.
EDIT: Wow! It took me so long to write my response (got a bit side-tracked) that Sabre beat me to it...
Originally Posted by DanGTP
