Having issues where Wi-Fi will only get about 8-12Mbps on average on clean install?
Applicable to all but this was with a Dell XPS, Intel Wi-Fi.
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Test before: fast.com 
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Add the following two lines to wifi config /etc/modprobe.d/iwlwifi.conf:
 options iwlwifi bt_coex_active=0 swcrypto=1 11n_disable=8
 options iwlmvm power_scheme=1
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Reboot 
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Test after: fast.com 
Source Ref: https://wiki.debian.org/iwlwifi