Does the exhaust manifold need to come off to replace head gasket?

[BillW]

I am replacing a head gasket on a 7mge and I am stuck trying to remove the 3 nuts that hold the exhaust manifold to the down pipe.

Why does the exhaust manifold need to be removed from the car to remove the head? Can I just detach the exhaust manifold from the head, leave the exhaust manifold attached to the down pipe, and remove the head?

If I need to remove the exhaust manifold, any ideas on how to remove the 3 nuts that connect the exhaust manifold to the down pipe? It's really tight in there. I have sprayed the nuts with liquid wrench and PB blaster and applied enough torque to round the corners of the nuts. Next, I'm going to try a nut splitter or a chisel to get the nuts off.

Any thoughts are appreciated. Thanks.