questions about an hx

ive read somewhre here in af that the hx motor (y5) runs on just half the valvs until it hits 2500 rpms, is this true? if it is can i just simply swap the ex ecu in to have it run like normal or do i need to swap the whole head, i have vtec well actually vtec-e and wasnt sure if i could just make it like the ex with the ecu. if i have to swap the head are there any other options besides the y8 head like maybe the z6 or wold the y8 hed be the best one anyways. i think if i get rid of this half the valves shit i might be able to get a little better launch cause i have the shittiest launch ever right now hah i wouldnt even call it a luanch but from a rolling start its not bad at all.