Is is a 180sx? If it is yes then some Later 180sx's with the round tail lights came with Black tops. No S13 Silvia came with a black top though. If yours has one its been transplanted. I was under the impression that all black tops came with VVT. Maybe you have a blacktop rocker cover on a red top motor?
And yes the ECU's changed when the black top came out they look the same and are wired the same but they don't work in the same way. Trust me I have tried and failed with mates cars, it don't work
. The red tops ecu is easily remaped. You need a badbiki daughterboard which plugs in to the stock ecu inside the box. It holds 2 eprom's which will enable you to hold 4 different maps. so you can have different tunings
. It is easy to install. all you have to do is remove 1 surface mount resistor and away you go. Of course you must go and have you car dynoed to see any real results from this. It's worth it though. All up it cost me about $600 which includes the daughter board and dyno time. Its is quite cheap and is hidden from the Fuzz. Where as the aftermarket managment costs heaps more plus installation and dyno time on top. Saying this though I now use a safc as I got one cheap from asia .