95 Discovery SE, 100000 miles. Occasionally after I start the truck there is an annoying whistle for about 4-5 seconds. It will not happen everytime and is difficult to pin point because it is brief. Mechanic says it is vacuum hoses as I think but they are all new (within 12000 miles). It sounds like it is coming from behind the intake and maybe below somewhere. If I tap into a hose and measure vacuum what should it read, or is there somewhere convienent to measure it? Can I download a diagram of hoses to make sure I got them all last time? Should I park it at the beach and start it everytime the girls walk by?

 

I like the beach idea.
Take a can of carb cleaner, and with the engine cold start it and spray all around the intake plenum and valley pan, if it is leaking the engine speed will change once it gets a whiff of the carb cleaner.
Then you know where to dig deeper.