Do I need a new server or is my site broken?

Hi I recently moved my website from a shared hosting package to a VPS after my host told me my database was maxing out.

I’m not set up on the VPS but I get frequent page load errors. Apparently system resource use on my server is at 96% and up which is causing the problem.

The obvious solution would be to upgrade servers, which I could do.

But I want to make sure the excess traffic isn’t being caused by a fault on my site – with a faulty plugin or database, for example.

Can anyone shed any light on what might be going wrong and how I could check it?

Or am I completely barking up the wrong tree and the problem definitely is the amount of traffic putting a strain on my server?

For reference, I am using the following plugins:

404 notifier, Akismet, Adsense-Deluxe, Auto Headline Generator, Breadcrumb Navigation XT, Classic Posts w/ List Option, Fold Category List, Google Sitemaps, Monthchunks, Random Posts, Recent Comments, Search Pages, Share This, Show Top Commentators, Spam Karma 2, Stick Post and and WordPress Database Backup.

(I was using Democracy and Firestats before the move but they didn’t work when I fired everything up again. I disabled the plugins but their entries are still in the database – am I OK to delete those?)