well my mani. on my 96 cx hatch was cracked. and thats what was causing all the problems. I know this sounds crazy but call a Honda dealer and talk to a service advisor. ask them about emissions warranty on your manifold and o2 sensor. If your mileage is right and it falls under that you'll get evrything replaced for free. I work at a Honda dealer so give it a shot. thats what happened to me.
o' rep points are greatly appreciated, especially if you get it for free