1994 Ford Ranger Vacuum Leak

I have a vacuum leak that I have not been able to find. I hear that this model had some problems with Vacuum. Is there a design flaw or weak point that others have found? How do I find Vacuum Leaks and where do I look for these leaks?

There is supposed to be at least 16 inches vacuum, but by the time it gets down to the transmission it is only 11 inches vacuum.