i have a 99 civic si with jdm b16 4-1 header blox intake manifold and greddy exhaust for the mods my o2 sensor isnt reading the first one or the second i know why the second dosent read its not there. Also i am obd1 running obd2 ecu my car runs like complete **** is this because of the ecu i have a obd2b to obd1 jumper and p72 ecu but ive been searching on hear and its says that ecu will make my car run like ****. Somtimes while driving ill get up to 60 miles per hour and it will the car will bog like its not getting spark or fuel and it runs really rich i keep fouling spark plugs they come out black *** ****

 

yea it does sound like an ecu issue. i have a b20 and i tried running the ls ecu on it and it ran like crap. since you have a 99 civic i would run obd1. also you can get a tuned ecu for your setup from locashracing.com and they will be very specific about how you want it set up.