Almost Complete! Performance Question?

I am switching the D15 in my 89 4 door DX with a ZC16 out of a 91 SI, I have all of the ECU stuff but am wondering how to make it VTEC and what is the advantage besides higher RPMS? I have also heard that getting an ECU out of an Integra would be a direct plug and play worth a few ponies. I am maninly concerned with reliability under extreme conditions. I road rally my car every few days here in Germany, (stationed overseas), and the D15 has done well but it is time for more horse power. Plus I just bought the SI for about 400dollars. So should I leave it with the stock ECU or scrounge around for the ECU out of an integra (what year and what should I be looking for) or would going VTEC be the right path? Or are they the same? Not sure any help would be great, especially since I am doing the swap now!!

Okay... about the higher rpms, you have been misled. The sohc vtec engines or mini-me (vtec heads with non-vtec bottom) still redline at about the same place... maybe 300rpms higher.... d16a6 ecu - 7200 rpm... p28 (vtec ecu) - 7500rpm The p28 is an obd1 ecu so rewiring is necessary to make it work. Search and you'll find everything you need to know. They did make an obd0 vtec ecu but it's pretty hard to find. Maybe it'll be easier for you to find in Germany. I've also heard of people using the old obd0 b16 ecus for sohc vtec applications. Also, I just thought of how the si in German may have the ZC dohc engine as the Si in Japan does. If so, you cannot put a vtec head on it.