Using performance monitoring tool \"New Relic\" I am seeing occasional (but too many) long delays in the \"AcquireRequestState\". I am talking about 10, 20 second delays, s
I suspect your stored proc change might be highlighting a slightly different problem in terms of session locking, we had roughly the same being reported for a different scenario, I'd seriously like to encourage you to test out the async session provider as mentioned here and making sure you use the concurrent requests per session app setting :
https://stackoverflow.com/a/55331786/7581050
Ultimately any long running process (in your case the stored proc change) is blocking any further requests for that session. Since this "block" is happening in a different part of the IIS pipeline, NewRelic simply records it as "AcquireRequestState"
PS: I know this answer comes quite late but I've finally found something that solved a similar problem for us and I suspect will help many people in the future.