Harry,
Turn up the boost and your wastegate will work, 7 psi is not enough to hurt anything if air fuel and timming is right. At 7 psi the gate has to much exhaust to try and control, don't need a bigger gate unless you only want 7 psi, but why?
Those gaskets may work N/A but that's it, if you make any error on the tuneup it's gone.
Cometic would be a good choice but will only work with a Kirby head, square water passage may not seal to round embosed gasket, thats the water hole at the spark plug.
Were did the gasket fail?
Good Luck
Harry
