Large RPM and Vacuum drop when shifting from park to gear
Sucking won't tell you a lot. The average person can only suck an inch or two of vacuum. I could make a lot of dirty jokes at this juncture, but that's something anyone could do.
Try blowing into the cannister....if it leaks, it's bad. If it doesn't, it's probably good. The next step would be to apply vacuum from a good source to see if it causes the arm to move in.