1998 Chevy Lumina Not going right away when put into gear

I changed the vacuum modulator...did not do the trick. When i pull the vacuum line off to the modulator, then plug it back in, it does go right away. Could there be a vacuum leak? I know the ignition switch is going out, anything to do with that? I have changed fluid and filter first to no avail. Please help to avoid costly repairs with a baby on the way!!!
thanks,
John