It'd be nice to review PSS sending of messages and handling/processing of messages, as there are a few unclear design decisions or bugs:

As an example:

1. enqueue is using a very large buffered channel with outbox
2. outbox is processing synchronously one message at a time.
3. SendRaw is not just sending, but also executing handlers synchronously.

These are a some of the issues I've come across while trying to understand why PSS gets slow when running Swarm with Push Sync functionality.

Changing these results in many failed tests, so before I spend more time on it, I think it'd be helpful to pair up with @nolash to understand better the request/handle flow.