Cam question?

Nice econo cam ya found there.

The intake duration will dictate the rpm band it works in. By adding a few more to the exhaust, your letting the engine breath out more exhaust making the new incoming charge cleaner for a better burn for more power.

This extends the rpm band a few hundred rpm's. Nothing is really in stone about it since this will change with the parameters of the engine and it's size and abilty of the equipment it has on and in it.