Use this plug-in to disable magpie rss cache and display feed content instantly.
You can use the built in installer and upgrader, or you can install the plugin manually.
You can either use the automatic plugin installer or your FTP program to upload it to your wp-content/plugins directory the top-level folder. Don't just upload all the php files and put them in
Activate the plugin through the 'Plugins' menu in WordPress
Go to Tools -> Disable RSS Cache
On the plugin admin page select Enable/Disable from dropdown menu and submit to save your options.
Browse web page that are showing content from external feed. You should see feed content immediately when new post arrive.