arvgta on "Disabling 404 handling completely"

Hello all,

my site:

http://4nf.org/

...uses the newest version of WP and some plugins such as W3 Total Cache.

My aim, just for testing purposes is to disable 404 error handling completely, i.e. to revert to "naked" 404 handling, which really throws a hard 404 error instead of handling it softly.

I've tried deleting the 404.php file in the theme and also disabling the W3 Total Cache page cache in vain.

I've also researched the web and the usual question seems to be the opposite, i.e. how to handle the 404 error "softly".

Any help is greatly appreciated!

Thanks in advance!