vtec wiring troubles

ive recently been working on wiring up my vtec through the ls harnes and cant seem to get it to work. do i have to have the knock sensor hooked up for it to work. and ive heard people talk about the vtec "screaming" when activated can some one give a better discription of what this sound is, my engine does make a higher pitched noise a little after 6grand but but it seems a little late for it to be vtec and i cant feel any difference in power.