Webfilter: Remove URLS very slow

I have a problem that removing a long list of URL’s
(for instance hpHosts - ad servers) lasts minutes, whereas the add
function lasts seconds. This way I can add a list but
when it comes to actualize a new list this is almost imposible.
This behaviour was not present in the v7. version.

Now I have more facts regarding this issue.
A List consisting of:
MVPS, hpHosts(ad servers), peter lowes ad servers and Dan pollocks
hosts Blocklists all URL’s are unique, put together wihout commentaries and
leading in a text-file:
add/import the list in a Category: 1 second o less
remove/import the list from the Category: 3 (Three) Minutes 4 Seconds of CPU (!)
This cannot be considered as a normal behaviour an I think this module
needs a code optimization.
I also have to say that the real-time behaviour is excellent, there
is no time-delay and in the log.File I see the result of all
the ad- and tracking-Url`s blocked.