The way I test for vacuum leaks is to use a propane torch, turn the tank on but DO NOT LIGHT IT. While the motor is running take the nozzle of the propane tank and go around the intake manifold of the carb and motor. If you have a leak it will suck the propane into the motor and it will increase the throttle, it will rev up slightly.
The old way that was used to test for a leak was to spray starting fluid around the area. Problem is that if you have a bad plug wire that is arcing slightly and you use the starting fluid well you are taking a trip to the hospital. Propane exposed to the air is not concentrated enough to cause any problem as there is too much oxygen in the surrounding air to cause it to ignite.
Last Edit: May 30, 2011 6:26:25 GMT -5 by 90GTVert