[Plugin: W3 Total Cache] Cannot modify header after uinstal

After upgrading to WP3 W3TC slow down my site…

So I uninstalled it and removed everything like cache-config.php and the entry inside the wp-config.php.

If I now loading my site I got this:
Warning: Cannot modify header information – headers already sent by….header.php
on top of every site!!!???

I only get rid of this Warning if I reinstall the W3TC and disable the cache function (’cause I don’t want it anymore).

So – what else does W3TC modify inside my Core or Database ?????

I just want nothing more than a clean deinstall of the plug.

cheers
thomas