Chrome valve covers (on a long inline 6) have a tendency to leak regardless if flange is straight.

Those chrome push in breathers like to leak also.

Recommend ditch both of those items.

Buy a good straight cast aluminum cover or a stock non chrome cover.

You can disconnect the secondary's linkage rod & see if there is any difference in power.

What color spring do you have in the secondary's diaphragm?

Having a stock camshaft really kills any real power to be made.

If you installed large valves, lumps, port the head & use a stock camshaft, that would not gain much power.

MBHD

12 port SDS EFI