if it is in fact a '96 than it is in fact obdII. Basically a scangauge (expensive version of Ultragauge) measures almost anything you can think of. An Mpguino is the preobdII version of a scangauge and is the only gauge that I know of that reads when your in leanburn which is why civics get such great mileage. Once you have an ultragauge, scangauge, or mpguino a vacuum gauge wouldn't help alot unless you really know what your doing
https://www.scangauge.com/
UltraGauge OBDII Scan tool & Information Center
MPGuino - EcoModder