I can give you an unqualified maybe. All of these parts take time, none of them take a lot of time, but if you add it all up, it could be a problem. The GeoIP database is pretty large, it has to be searched with every request if it is enabled. The regular expressions in the WAF Blacklist would take a little bit of time for each line in the blacklist. If you have thousands of blacklisted IP addresses, each of those take time.
We're talking milliseconds for each of these, but if you pile up enough milliseconds, you get a noticeable delay. From your description, I can't really tell if it is Admin Tools. I don't think so, but it is possible, depending on your setup. You can disable the System - Admin Tools plugin to quickly disable Admin Tools in order to test the theory. This disables all of WAF and the GeoIP blocks. Obviously, you don't want to leave the plugin disabled for a long period of time, this is just for a test.
On your GT Matrix, the easy way is to check the server error log to find out which file is throwing the 403 and double check the permissions.
Dale L. Brackin
Support Specialist
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