You lose torque below 3000rpms with it disco'ed, for the reasons noted above, mainly it defaults to the short fat high rpm runners instead of the long skinny low speed runners. I've seen believable claims that the correct length tube is worth 2psi at the valve. Think about what a turbo motor does with an additional 2psi of boost, and that's what you are giving up on the bottom end by discoing the vac actuator. WOT power above 3000 will be the same either way.

In order of best>worst,
install a new lower plenum - not terribly hard, just tedious.

repair the old lower plenum bushings and replace the shaft butterfly screws. Cheap and tedious.

Disable the actuator by discoing the vac line and wire the arm into the short runner position (against return spring pressure...)

Do nothing until the motor eats metal instead of air and fuel, and does the big clanky mucho$$$$$ thing.