I have yet to see a intake leak produce anywhere near 19-21 in of vacuum. Thats 20+ years in the automotive repair industry. Not to say its not possible. Just saying I have yet to encounter it.
Tony.. I hear ya. These 3800's though are pretty good at maintaining good vacuum with a decent amount of leaks. Even then..I've found battery cable corrosion causing an issue with lean bank 1. So hey..in that case..it wasn't even a leak.