I don't know the shape of the '96-'97 Del Sol ECU's, but if they would fit, those would probably be your best bet. A P72 will definately affect your performance. A B18C1 does have a dual stage manifold, basically two paths for air to go, the computer can open and close one at around 5700 rpm, but that wouldn't really affect you. What's killing you is the B18C1's VTEC changeover point is at 4400 rpm, while your B16A cams are designed for a mid 5000 rpm changeover. You've probably got a big hole in your midrange pull because your forcing the engine to run on the big cams when they're not designed to operate that low.

You could use a P28 that's been reprogrammed to control a DOHC VTEC engine, but you will loose your knock sensor functionality and maybe others depending on what program you use (avoid any that raise or remove your rev limiter unless you've upgraded your valve train to handle the extra rpm's). There also may be legal issues using an older computer in a newer car, but those depend on your local laws. I'd try to see what you can find out about a '96+ Del Sol and if that computer would work first. Even if you can find one in a salvage yard somewhere, have them describe the shape of the ECU connectors and see if they are the same as a '96-'98 Civic (sorry, but I don't know if they are or not). Good luck.