Lets assume you are going to ruin the pipe. They are easy to find. Will Tillery is my first call.

Obviously you want to try things that will dissolve the corrosion between the pipe and the intake. This will sound crazy, but I would pour some white vinegar on it and let it sit for an hour. Follow that up with your favorite penetrating fluid (PB Blaster, Kroil, ATF+acetone, etc). Maybe things get easier.

If not, you are trying to separate the flange at the end of the pipe from the lower intake manifold. If you can find something akin to the end of a claw hammer that will wedge in there you can force them apart. Something like a bearing puller/separator kit or even a ball joint separator. Some imagination goes a long way.

If you wind up damaging the lower intake that wouldn't be the end of the world. They aren't overly expensive either in the grand scheme of things.

 

It was stuck on mine too when replacing it a few years ago. I ended up removing the intake manifold so I could apply heat and that worked great.