97 Civic EX-megan 4-2-1 header, WS2 exhaust system, AEM SRI. I would like to upgrade my ecu & obd but I dont know which ones I should be looking for, could you guys offer some direction. Will this throw off my fuel mileage or make me start throwing codes if I change my ecu & obd, and can I expect any noticeable gains if I do this.

 

you need an OBD1 P28 ECU (the one D16Z6 uses) and a obd2-obd1 conversion harness
The ECU needs to also correspond to your transmission.
it'll work fine


You won't see any gains unless you chip it (a real chip, like phearable.net chips... not the ebay ones), but the gains from that will still be very minimal.

you can buy the ecu harness and the chipped ecu at phearable.net and tell them what you have. You might get a tiny bit of gains (unnoticeable), but not really much because you just have bolt ons.

the ones from phearable are all for manual transmission, btw


personally, i'd take that money and get a magnaflow direct fit high-flow catalytic converter instead on summitracing.com
you'll probably see more gains from that than a chipped ecu/OBD1 swap