activity-log.com

Plugin allow you to run most important test for performance: request time, number of database queries, memory usage
You will be able to detect plugin which cause troubles and result with longer waiting time for request results
Testings are executed based on your homepage
<iframe loading="lazy" title="WordPress Profiler – What Slowing Down Your WP" width="750" height="422" src="https://www.youtube.com/embed/3hJbClFbw5s?feature=oembed" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" referrerpolicy="strict-origin-when-cross-origin" allowfullscreen></iframe>
How to use it?
In Dashboard go to Tools->Profiler What Slowing Down
Click on run test on all plugins (first link) and then near wanted plugin, run few tests and compare results
If you get significantly lower results, means that this plugin causing slowness
Hint: Lower numbers are better, means that page load faster without this specific plugin

Profiler – What Slowing Down Your WP

Plugin allow you to run most important test for performance, request time and number of database queries With this Plugin Performance Profiler you wil …

stasionok

With this simple plugin you can restrict extra external requests made with internal WordPress WP_Http class. 
Just put in the filter rules field what you wish to restrict. One url part or url regex per line. 
By default, the plugin returns WP_Error answer for restricted requests. But you can put in response your custom response data.

ROB (rat out blocker)

Restrict execution of certain external requests with partial url or even regex to prevent personal data leakage (as example)

Profiler – What Slowing Down Your WP vs ROB (rat out blocker)