cache?

I am writing a new plugin what alters the content of the rss feeds. If I make any changes it does not have any effect.

Than I go to /wp-blog-header.php and before the wp() call I put a die(‘1’) call, reload the page, delete the die call, and reload again. After this I could see the result of my changes.

I think that is beacuse some caching. Is it a way to turn it off? It is really hard to debug like this.