Strange requests in apache2 status

Strange requests in apache2 status

I own OVH dedicated server running Debian 6, Apache: Server version:
Apache/2.4.6 (Debian). I moved my website to this server, but it works
really slow. CPU usage is never more than 10%, typically 98% is idle.
However apache2 is not responding or it does after 10 - 15 s. It does not
matter whether i try to load static file or php script.
In mod_status i can see:
Server Version: Apache/2.4.6 (Debian) mod_fastcgi/mod_fastcgi-SNAP-0910052141
mod_fcgid/2.3.7
Server MPM: prefork
Server Built: Jul 23 2013 11:42:21
...
256 requests currently being processed, 0 idle workers
Some of the request are quite normal, but there are also some strange like:
160-0 - 0/0/19 . 0.07 464 278808 0.0 0.00 0.82
69.163.243.40 sth.com:80 GET /?198740=-666120 HTTP/1.0
191-0 - 0/0/13 . 0.07 464 280846 0.0 0.00 0.53
69.163.187.77 sth.com:80 GET /?-161926=633136 HTTP/1.0
Sometimes there are about 200 such positions...
EDIT
I menaged to increase workers to 1024 and now it works fast, but still the
problem with strange client occurs.