To cheak cracks and leak's, get soem aero-strater or 'start-ya-bastard' and spray around manifoild: rev's rise then you got problem.
For the high idle, check that when you have blocked up the vacuum lines you have not simply hooked up a air entry to a vacuum hole... MANY people do this (I had one for a while).
So for each line block it off seperately rather than routing one line to another one...
I went from a high idle of about 1400 to 800. It idles from 700-900 dependant on weather conditions (and accessories on) as the factory VSV (idle up) is not hooked up.