pipe popping
Do the Exh port on the head look even, aka color texture exc. Can you get a mirror and actually look at the exh valve and seat area.
If i couldn't find any difference between #7 and 1,3,5 I would NOT pull the head!
Did you look at all the welds?... collector or defuser (Sp) weld.
Maybe bolt a block of wood to the header ports and then another one over the outlet of the header/collector. Then, drill a small hole in it and install a air fitting. then just add air pressure to see if you have a leak any were
YOUR LEAK DOWN TESTER WOULD BE IDEAL FOR THIS TEST. As you could regulate the pressure in the header.
4 feet of a 2x4 and drill bit and some nuts and bolts would get the job done.
Way less time then pulling a HEAD.........