Nissan Repair: 99 Quest / Villager, vacuum hoses, rubber seals

Question
Hi
I need help. I have a villager that has a Nissan motor in it. I replaced the motor 3 weeks ago. I had to remove the Plenum Intake to use the wiring for the old motor and the fuel rail. Now I have a hissing noise. I have replace the Plenum Intake gasket and all the Vacuum hoses on the motor. I even changed the rubber seals behind the EGR Valve spacer and the throttle Body gasket.
I still have the hissing noise and the rough idling. The check engine light is on and it said the O2 Sensor was bad and I replaced it. What else can I try?  

Answer
Walter,

I would get a fire extinguisher and an assistant to hold it while you spray carburetor cleaner on the suspect areas.  If the idle increases you found the leak.  Correct the leak and check it again.  It does not take too much cleaner to find the leak so use sparingly.