High Server CPU after 16.2.1 Upgrade

My first question back to them, would be

'What's in the access and error logs for your apache server'? Both before and after the BigIP upgrade

If it's the BigIP then the traffic profiles hitting the apache will be different. 

Better check from the servers whuch process causes the issue not on the F5. The issue could be that F5 now uses more complex SSL ciphers or something needs to be changed in the server side TCP profile on the F5 device to optimize the traffic.

https://support.f5.com/csp/article/K50411377

https://support.f5.com/csp/article/K72605755

Still check the F5 LTM logs for some new errors with the VIP/nodes/pools/poolmembers and also see the f5 interfaces for some errors just in case.

Sorry I couldn't follow the context, is the load high on the servers or on the F5 ?

If it's on the F5, run the top cmd and see which deamon is causing it. See if it's the odd or even cores, so that we'll know if it's the tmm or non tmm.

Some good feedback here. I'd add:

• First off, do you mean release 16.1.2? There isn't a 16.2.x.
• Secondly, using default profiles in the config can create unexpected behaviors during major upgrades, as options within them can and do change over time. I'd review the tcp and server ssl profiles first, and perhaps your monitors as well to see if any of those are different after the upgrade. 
• Lastly, if you haven't upgraded the standby box yet, take a packet capture on your upgraded active device, then fail over to the not yet upgraded standby device and take another packet capture so you can compare and analyze between the two environments.