Joomla 1.015 speed

I have version 6.0.1 sef advance on a joomla 1.015 website.
When I have sef enabled my site goes to a crawl, when I disable it it goes fast.
I cleared the cache and shortened the time. No change, Turned cach off, no chaange.
Turn sef off real fast, turn back on, real slow.
Any ideas?
I have read all the posts and the only thing I can seem to find is that you found sites having DDOS attacks, I don't know how to check for that.

I will be moving my site to Joomla 1.5 as soon as a main component is upgraded. That may be another month or so.
Thank you

Try turning off SEF Advance, leaving core-SEF working to see if it's mod_rewrite issue.

To check if it's DDOS attack on your URLs you can use .htaccess to deny access from all but your IP address and test.

Tried turning off sef advance and leaving core sef running. It is fast. Turn sef on with core on and it is slow. does core sef need to be off with sef adv on?
Can you tell me the commant to put in .htaccess to lock all ip out except mine?
Thank You

SEF must be on in global configuration.

Try:

<Files *>
order deny,allow
deny from all
allow from 123.123.123.123
</Files>

Replace 123.123.123.123 with your IP address.