Xcart has caches yes one way to clear them is:
http://5dollarinkcartridges.com.au/newsite/cleanup.php
But I think the issue is just that we are working with the wrong tpl. I doing my best to teach you what I know of this system, sometimes I forget that people need to know the basics first. The first thing I do is make sure I am working in the right tpl. It is probably customer_manufacturer_products.tpl just as you said.
You can use webmaster mode to determine what tpl's are being called on what page. It also gives you a list of variables and there values. Lets make sure that we are working in the right section, when you referred to products_list.tpl I immediately assumed that you were working inside a category. (oops)
Familiarize yourself with webmaster mode, take note of all the templates on the page and what each one controls.