[priobe]

Here is an idea.

Take the header and lay a straight edge across the header in 3 places (straight across, bottom to top angle, top to bottom angle)

If possible do the same for the head exhaust to make sure both surfaces are flat.

Use a belt sander on the header to get it flat.

You can cut the header per port but if the worpase is on the port of the head you are out of luck.

I resurfaced my headers and head when it was off and I have no issues with leaks