I'm having trouble figuring out why two cylinders would be causing issues. If it was a bad valve, one cylinder would seem more likely.
Maybe try putting air into one cylinder and see if some comes out of the adjacent spark plug hole? Maybe the gasket is blown between two cylinders?
I had one valve that was bent, it looked like an upside down mushroom, it was a soup bowl shape instead of flat. A headgasket failed, the cylinder filled with coolant and bent the valve.
Another time I pulled a piece of gasket material out, that was stuck between an intake valve and the seat. I caught it early and there was no real damage.
If I was sure of my findings, I'd pull the intake/exhaust manifold off. You can see most of the intake valve. Maybe put a light coat of talcum powder on the intake, them blow some air into the spark plug hole.
I'm not one to jump to conclusions, I'd rather spend the time being sure, before I waste the time guessing and pulling unnecessary bits and pieces off the motor.
Except for the end studs and maybe the downpipe to exhaust manifold bolts, pulling an intake/exhaust is no big deal. I don't unhook any thing I don't have to, the fuel line, some connectors and vacuum lines, then unbolt it and flop it over onto a blanket on the passengers side of the motor. Just be careful with the harness and try to avoid kinks and unnecessary stress. I can have it off in half an hour and on in an hour. Two people to torque it back down properly is a big help, one to hold the socket on the bolt and the other person to work the torque wrench.