help me improve my speeds please

I am trying to improve my speeds utilizing this site I have been able to get it down from 10+ seconds to 5-8 depending on the time of the day that I do the test and what browser I use.

Any help would be apreciated I have a VPS and my time to first byte seems to be a little high, I cache my JS, CSS, and images, I also compress my JS and CSS, but still seems to be unrespectable time loads HELP PLEASE

here is a link to my latest test

http://www.webpagetest.org/result/131009_15_2XD/

Thanks
J

I cannot connect to your website at all, at the moment:

[quote]Service Temporarily Unavailable

The server is temporarily unable to service your request due to maintenance downtime or capacity problems. Please try again later.[/quote]

Have you enabled keep-alive yet, as the WPT results suggest?

Judging from those results, your server’s processing PHP appears to be laggy, and since you’re minifying lots of resources through a PHP script, your otherwise static resources now also have a large TTFB.

You mention you have VPS. Is it often under heavy load, as the above error suggests?