Try this:

```
p2p-use-ipv6=true
prune-blockchain=1
sync-pruned-blocks=1
in-peers=1024
out-peers=1024
```

Depending on how you are running the monerod, you will need to raise LimitNOFILE / ulimit -n, the safe value for the config snippet above is 4096 

 Trying this now to see what happens. Didn't know about sync-pruned-blocks. 

 I can't tell if it had any improvements. Still have some part of the day with higher sync rate and others where it goes quieter.