@joeltom21, yes you need to open up your case. But, if you are in US, you can make a Genius Bar appointment at apple store and ask them to open you laptop and clean the fans. They don't charge for this and very safe way to do it as they have appropriate pentalobe screwdriver etc. I had exact same issue with with my MBP, where connecting external monitors would make a 2019 model useless duet o kernel_task cpu usage. When I got the fans cleaned at Apple store, my MacBook was back in game. I am now able to connect two monitors with no issues whatsoever. My MBP runs without any noise where as earlier it used to due to the dust trapped in fans reducing their cooling efficiency.
santoshm
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