Chris
As you seem to have done all the right things to allow Apache and IIS to coexist I think this is more of an IIS issue and for that you will have to find another group to help you out.
To be absolutely sure, if you make sure WAMPServer is not running then Apache will not ever be in the mix.
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(Windows 10 Pro 64bit) (Wampserver 3.3.4 64bit) Aestan Tray Menu 3.2.5.4
<Apache versions MULTIPE> <PHP versions MULTIPLE> <MySQL Versions MULTIPLE>
<MariaDB versions MULTIPLE> <phpMyAdmin versions MULTIPLE> <MySQL Workbench 8.0.23>Read The Manuals Apache --
MySQL --
PHP --
phpMyAdminGet your Apache/MySQL/mariaDB/PHP ADDONs here from the
WAMPServer alternate Repo-X-X-X-
Backup your databases regularly Here is How dont regret it later! Yes even when developing -X-X-X-