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Spray the gasket with penetrating oil several times over a few hours.
Last resort, with body seperated from throttle assembly, take a small scew driver at the bottom of the metering block where it won't be seen and pry it apart.
Now about that power valve. If it is bad, the fuel will not be coming out of the venturies, I don't believe. It will be coming in below them.
You can switch parts between the front and back bowls to find the problem also or just replace needle and seat and then float.
To verify the float setting is not too high, turn the bowl upside down and the top of the float should not be below the top of the holes for the screws that hold the bowl on.
Double check your fuel pressure. Reset it lower. 6-7# is normal.