Hello, I have been looking for a vacuum leak for weeks. My engine runs well but idle is not what I think it should be . The engine has a miss and the sound at the tailpipe is not smooth. The car has new wires ,plugs, pertonix ignition , new cap and rotor. The engine compression is fine. I know that device to check the exhaust is used when setting the idle screw on the ECU but I have set the screw by ear. At this time I have the screw set to the full rich position at which point the engine runs best. The plugs are clean and not carbon fouled my question is, is it ok to run the ecu in the full rich position all the sensors check out well within spec with the ohm meter . I have checked all over the engine for a vacuum leak I have used carb spray , propane , and water . From time to time I have found some small leaks and repaired them but the engine has a sound unlike any other B20 I have heard there is a low whistle that can be heard at idle and when the engine is shut down almost like an in and out noise. I do not expect any answers but I am just throwing it out there maybe someone has had the same noise. Thanks in advance for ANY reply.