Insane memory usage

I started to run a phpbb3 and wordpress blog (without cache) on my first webhost.

After a bigger visitor wave (not too big 50 at a time on page) caused account suspension, cause I overused server resources and they are suspecting the responsible is this mod.

Okay no problem, I bought a VPS.

Installed linux, apache, etc. made diags.

Then I realized what the previous hosting company spoken about:

WordPress process WITHOUT bridge:

http://img600.imageshack.us/img600/7269/94295653.png

WordPress process WITH bridge:

http://img14.imageshack.us/img14/9974/76253431.png

This is a really really really big difference.

Here is my stats from bridge settings which is doesn’t really matter because they throw me out from the previous (Hostgator):

http://imageshack.us/content_round.php?page=done&l=img96/410/70734718.png

Do you have any idea which causes this huge memory loss?

http://wordpress.org/extend/plugins/wp-phpbb-bridge/