VTEC not kicking in????????

I asked this question already from my friends profile... but I have a 89 crx hf with a 92 Si conversion... one guy told me that D16a engines don't kick VTEC in... but to be honest i think i have a D16z6 I just said D16a because i didn't think it would matter that much.. my question is how can i make the VTEC kick in... ive been ped 6100 rpms so its not like i havent tried.. some guy said I should buy the 92 civic Si ECU then it might work.. any other ideas... maybe missing something?