I have been using shared hosting for years... I have 4 vbulletin sites along with a few other forum softwares & a few html sites on one hosting account & 2 vbulletin test sites along with a few other test forum software & many scripts running. I have no issues at all. And I have vbpager installed on every vbulletin site but 4.0 versions. I also have comet chat installed that I host without issue.
Your host has added to many customers to the box you are in & goes after the resourceful sites because they are slowing down the server.... Ask them to move you to a better box.

I have found that only allowing user sigs to show only once per thread page will greatly reduce your usage. Also, allowing members to have live feeds to sigs will slow down showthread big time, so try disabling all usergroups the right to have sigs for a few days to see if that helps.
If you have other sites within your domain space make sure they do not have scripts running at all times.

In your cpanel, scroll to the logs section and click CPU Throttling. Post results here please.

After that scroll down to the Advanced section & click Process Manager. How many processes is your site running and how long have they been running?

You will see a few for vbpager.... I know the pager well & can help you reduce some of the processes with simple default settings & some code changes.
Your issues are fixable so you can stay where you are.

Go to phpMyadmin in cpanel, click on your database & optimise all tables with overhead...

I think you should get in contact with Leon over at http://www.ufhosting.org/ hosting vbulletin websites is one of his specialties.

as Tim (Blind-eddie) says the box may have been oversold, its very common, enter your ip or domain here http://www.myipneighbors.com/ or http://www.myipneighbors.net and it will show you how many sites are on that box (the latter shows whether it's a site that is linked to from one site on the box to another).