Plugins causing server overload

I have a news aggreagator site that is using Autobblogged plugin to publish feed articles excerpts and WP to Twitter to send the link shortened with Bit.ly to Twitter.

I have always used Autoblogged alone and it never caused a problem. Now my provider suspended my account twice for server overload and the third time I’ll be kicked out…

Do you think WP to Twitter is the issue? If so why and how can I solve it?

Thanks