How do u get the old gasket off while manifold is installed?

 

Are you talking about the little metal donut ring thing that seals where the manifold attatches to the down pipe? Just PB Blast the bolts, take them out (and replace if possible), and then I think there is a hanger near the middle of the long part of the down pipe. Get it off the hanger and you should have enough droop to swap it out.

 

That's the one. And then cut off the old one? Pulling if off doesn't seem to be an option.

 

If it is welded or rusted in place, then yes, you might have to cut and pry at it.