Ok guys, I have a 1996 SE-R, with BB swap for the last 5 years or so. Car starts fine, drives ok, kind of has a hesitation/slight bucky when cruising. Anyway my question is that I hear a hissing noise coming from under the car in the rear, like around the fuel tank area. Now I have had a Walbro fuel pump since the swap was done, and I know what the fuel pump noise sounds like when you turn on the ignition and it pressures up, but when the car is idling this is not the whine I hear, like I said its a hissing sound almost like an air leak, and the hissing sometimes weakens or gets stronger if the revs go up or drop. Has anyone heard this before, any suggestions on what I can check, this has been doing this a couple of months.