I don't think any of the us 88-91 civic's had a vtec harness. They didn't come vtec from the factory! One of the ways to activate vtec would be to get an RPM switch, Or if you have a chippable obdo ecu then you can have it chipped for vtec. I plan on having my ecu chipped for my application so that I wouldn't have to get an RPM switch as well. Just a few cheaper options that might work out better than trying to find a vtec harness for a 88-91 civic.