Hi,
I have an Accord Type R which has recently had a Euro R engine installed. The car is making a loud constant "Hissing" noise coming from around the inlet manifold area. The noise does not change if the car is revved. It sounds like air is being drawn in other than through the throttle body. All vacuum hoses are fine and the airbox is tightly sealed. No CEL is being shown and the car seems to drive ok from a short test drive. Another inlet manifold has been tested but the noise remains. Does anyone have any ideas as to what is causing this?

 

check the vacuum port on the manifold flange under the center runners. Sounds like you are missing a vacuum line that assist the fuel injectors.