Let's look what I do:
I am working with the <b>wfdownloads</b> module. I want to change the way the list of documents is displayed. So a bit of tuning of html/css.
The viewcat.php calls "$xoopsOption['template_main'] = 'wfdownloads_viewcat.html';" ... so I guess it's the file in the template subfolder (of the same module).
Here, just for a try, I delete the whole code. And safe the file.
I delete the files in the template_c folder. I delete the cache. I load the page in another browser.
Still, the whole code displays...