Have you ever felt the need to wait for a while for the rev counter to drop while changing up a gear? Well, that’s called the Rev Hang.
It is mostly done by the tuning of the ECU by the OEMs to have a restraint on their emissions.
Here’s a small blog which explains it all:
The only way to fix it is to retune the ECU or simply leave it if it doesn’t effect you that much. But surely, that wait must be quite frustrating!