I made this tool at work to check for intake leaks and leaks in the vent system.
Some people will by Fog machines in shops that will do almost the same thing.
This is only a picture of the tool and a small idea of how to use it.
This can only be used with a air compressor.

So I got the round plastic cap looking thing from a New fresh air hose that was purchased from the Dealer for a Customer.

Then I got a pressure regulator with a gauge on it.
Also got some couplers that matched the air lines at work.
I installed the couplers on the regulator first. one female and one male so it can be installed inline with the hose.
I than took the plastic cap and drilled a hole in it. I drilled it small enough that the coupler could be screwed into it.Then took a female coupler that had female threads in it rather than male threads and screwed it on the male part of the threads on the cap.

Then when you need to check for an intake leak or boost leak you can remove the induction hose from the massflow and slide the cap into the hose and clamp it in there.
Then remove the oil cap.(I loosen the cap and stick a rag between the cap and motor to prevent splattering oil when the cap vibrates)
Then plug in the hose to the regulator setup.(Make sure the regulator is turned all the way down so no air comes out. Then turn the regulator up to about 3 PSI 4 max.
Then listen for leaks. If you can't hear anything leaking get a bottle of soapy water and spray all connections looking for bubbles.

Fix leaks as needed.

Here is the pics of the tool.

(IMG:http://img.photobucket.com/albums/v624/mustang8719/Picture001-2.jpg)

(IMG:http://img.photobucket.com/albums/v624/mustang8719/Picture002-1.jpg)

(IMG:http://img.photobucket.com/albums/v624/mustang8719/Picture003-1.jpg)