if still enabled, you can try disable "Acknowledge on Push" in virtualserver's client (side) tcp profile, so that f5 will acknowledge client's push without waiting for first segment of server response.

https://my.f5.com/manage/s/article/K50411377#datatransfer

Are you using connection mirroring on the VS also?  The Active system has to hold the connection until the standby acknowledges the mirrored connection info.

https://cdn.f5.com/product/bugtracker/ID512490.html

I tried with/without mirroring, disabling mirroring in sys database, no impact on latency.

Hi Anatoliy,

The tcp-lan-optimized profile is a preconfigured profile type that can be associated with a virtual server. In cases where the BIG-IP virtual server is load balancing LAN-based or interactive traffic, you can enhance the performance of your local-area TCP traffic by using the tcp-lan-optimized profile.

The f5-tcp-wan profile is a pre-configured profile type. In cases where the BIG-IP system is load balancing traffic over a WAN link, you can enhance the performance of your wide-area TCP traffic by using the f5-tcp-wan profile.

Could you please try to use other TCP PROFILE tcp-lan-optimized or tcp-wan-optimized based on your requirement.

Recommendations

F5 recommends that instead of modifying a default profile, you create a custom profile using the default profile as the parent profile. You can then modify some or all of the values defined in the custom profile, while leaving the parent profile settings at their default values

https://my.f5.com/manage/s/article/K7406

K7406: Overview of the tcp-lan-optimized profile (10.x - 12.x)

https://my.f5.com/manage/s/article/K10281257

K10281257: Overview of the f5-tcp-wan profile (13.x - 15.x)

Please let me know if it helped resolved your issue or still facing issue.

HTH.

🙏