I need some ecu help guys. I have a b18c in my 2000 civic si. It has the stock ecu and I am wondering what ecu I need to switch to to get it running better. Any info would be great. Thanks guys.

You would defintely need the p72 ecu from the b18c swap because it is the only ecu that can run the secondary butterflies that are equipped in the intake manifold. You would be using your old harness and adding any wires that you need from the ecu to the engine bay. You will probably need a jumper harness to convert to whatever obd system your new ecu is using. I recommend a obd1 ecu and a obd2a-obd1 ecu jumper harness. The obd1 ecu is less emissions friendly and doesnt throw as many codes, plus they have the ability to be tuned and chipped.