What car do you have, and what year engine is it? The RPM switch he is talking about is to activate VTEC, it just turns on at a certain RPM. It's a cheap, and VERY ghetto way to do that. You shouldn't be using a non-vtec ECU for a vtec engine, the ECU won't be tuned for the new engine. The better idea is to get the proper ECU for your car, or get an ECU chipped to properly run the different engine. That is the best choice, and the safest way to go.
Another option is to get a VAFC, it can be used to activate VTEC and do some fuel tuning to conpensate for having the wrong ECU.