you can go obd1 manifold and stay obdo if you use an obd0 dizzy and ecu. the only things that have to match are the distributor and ecu. a nice upgrade to consider would be a d16z6 manifold with a d16a6 dizzy and pm6 ecu. with that you dont have to worry about gettin a resistor box for injectors and you can remove the mapsensor/purge control from firewall which looks nicer caseu there are less vaccum lines. the benefit of goin with the z6 manifold off the bat is if you do decide to go obd1 in the future its less money you have to spend on buying 2 manifolds. but id recomend skipping the middle man so to speak since the obd1 intake manifold will work with obd0 ecu. thats exactly what im using right now. another benefit of the d16zg intake manifold is the bigger b-series throttle bodies bolt up to them which is not possible with the obd0 si manifold.