The sound you hear from your cardo is perfectly normal. The difference or the reason for the sound is the frequency that it fires (the pulse) The Zmax VAMO and the AnyVape CVI all appear to fire in the 30 - 40 mhz, very low which is why you hear it. While the ProVari eGo Twist and many others fire in the 800 mhz range. It does not hurt a thing just takes a while to get used to the new sound.
Glad to hear all you guys like your new UNITS lol.
vape Hard Life is Short.
Josh