Percona Server 5.7 replication is slow than 5.6, huge delay

We are plan to upgrade Percona Server 5.6 to 5.7 because of the replication delay problem during peak hour and hope 5.7 MTS will fixed the problem. We make a test at stating server, before the upgrade we can do about 6000 insert/s without delay. But after the upgrade we can only do 3000 inserts/s. The 5.7 version is 5.7.13-6-log. we only changed these parameters:

slave_parallel_type changed from database to LOGICAL_CLOCK
slave_parallel_workers changed from 2 to 8 // we only have 2 databaases so we use 2 in 5.6 for parallel replication
sync_binlog changed from 1 to 0 //with 1 it is even worth

Is there anything need to change?