It sounds like the carb intake manifold seals are failing. You must be certain to tighten them down equally, and slowly, to draw them at the same rate up to the heads or else the seals may shift.

I believe the intake leak test should stall the motor if using carb cleaner sprayed on a leaky intake manifold. Carb cleaner will cause your motor to stall, not rev up.

If you use standard brake cleaner or propane it will rev up and may even ignite a fire. These are some other aerosols some others use for the test.

 

I would also replace the carb to manifold gasket. I've been though a few of them, cause issues at idle and can start to backfire when rolling on the throttle.

 

Thanks guys. I'll do the test for sure.