I'm the one that introduced the "vacuum suck" method of cleaning the intake manifold. It cleans more in that it also cleans the combustion chambers as well as the intake and exhaust ports.
It does not matter how you introduce the cleaner into the intake manifold as long as you can properly control it. I find it easier to control with a vacuum hose. Although it is hard to find, Berryman actually makes a kit with a hose for doing this, however it is intended to use the hose or tube in front of the throttle body. IIRC the kit also includes some method of controlling the flow of the cleaner. You might find it with a Google search. It probably would do a good job, but I didn't need it. Part of what is essentual is that you find a point to introduce the cleaner that will distribute the cleaner evenly to all cylinders. Using the two vacuum ports on top of the intake manifold will do that, especially if you use about half the cleaner on each port.
As far as changing the oil or spark plugs immediately after, it is not necessary. If I am doing this at the same time I'm doing a spark plug change or oil change, I will do the intake cleaning first, but it is not necessary.
If you have any other questions, please ask. You can PM me if you wish.
