I deleted some contacts and they aren’t deleted in the other app

That’s because PieSync doesn’t sync deletions. It’s a safety measure on our end to avoid PieSync from being able to wipe out (parts of) their databases completely cross-connections/in multiple apps, when a manual error is made for example.

Once you delete a contact, PieSync will also not try to recreate said contact. The contact in the other app will become excluded. 

PieSync does have the syncing deletions feature​ in some of their integrations. This tags the deletion from app A in app B. It will never automate hard deletes but this way you can check the 'trash' segment in app B and hard-delete manually after reviewing. We should be able to do this for most connections with Command.