Do you have any other symptoms of vac leak, door locks not functioning, hard breaks, or engine not shutting off?
I would first go throught the vac system. Make sure you vac pump is supplying enough vac and that there aren't any leaks. Then I would make sure to check that the transmission modulator isn't leaking. Also make sure you vacuum control valve is functioning properly. If all that checks out you might look into a few things.
The B2 piston affects the 1-2 shifts, so replacing that may solve that problem.
The K-1 spring works on the 2-3 and 3-4 shifts and replacing that may fix you 2-3 problem.
The delay shifting into gear may be the bushings on the gear selector. Might look at those and see if they need replacing.

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