[Plugin: Jetpack (infinite scroll)] single category display on home page

I’m trying to have my home page display only posts from my “featured” category, so I added this query to index.php:

<?php query_posts($query_string . ‘&cat=303’); ?>

When Jetpack’s infinite scroll is inactive, it works fine. However, with infinite scroll, it displays the right articles at the top of the page, but as soon as it loads new articles (as you scroll down) they come from all posts and all categories combined.

Strangely enough, this is only the case on the front page. Infinite scroll works fine when i go to the category:
https://www.stanaron.com/category/featured

Is there a problem with my php query? How can I make my home page behave the same way as my /category/featured page with infinite scroll?

Thank you