We managed to resolve the “Poor Performance”, but we had to do a lot of reading, it was good that the profiler pointed us in the right direction suggesting to set this value MinWorkerThread
• This request is spending time waiting in the CLR Thread pool queue. This has happen if there is a burst load of requests coming to the process or if there is HIGH CPU on the overall instance.
• Recommendations : Increase minWorkerThreads setting if your application is getting burst load of requests.

But it was difficult to determine this value.

The following Very old link – actually helped us to understand what this values should be and fine tune it for our environment.
• 07/14/2010 Retired Content - Chapter 6 — Improving ASP.NET Performance
o https://docs.microsoft.com/en-us/previous-versions/msp-n-p/ff647787(v=pandp.10)#threading-explained
 Threading Explained
 Threading Guidelines

Serious Suggestion: This information should be easily available and MSDN help for this method ThreadPool.SetMinThreads should have a link to it. This situation can actually affect Products/Projects/Companies.