HELP: Been all day trying to LOOSE the intake manifold--->STUCK!!?

I think what you are removing is what Haynes calls the "collector" and I called the "plenum" when I had a similar engine in my 1984 300ZX. That part sits on top of the actual intake manifold. If yours is the same the throttle body comes up with the plenum, and lifting repeatedly on the throttle body with your hands should loosen it eventually.