Well, someone already reported this behaviour:http://www.amiga.org/modules/newbb/viewtopic.php?topic_id=30274&forum= 22#forumpost367080
but I am not able to reproduce it. AWeb runs just fine here. The only slowdown I noticed is during the first inicialization of AWeb itself. That's because AWeb loads all the truetype fonts at the beginning.
Anyway, it seems the slowdown might be caused by truetype fonts used in AWeb. There are few possibilities how to solve this situation:
1) You can always revert to your non-truetype config by MotpheuZ tool, but this will disable all truetype fonts, not only those used in AWeb.
2) You can use non-truetype config for AWeb only. Rename "browser_noTTF" file to "browser" located at "AmiKit:Prefs/Env-Archive/AWeb3/" drawer, but please keep also the original "browser_noTTF" file there, otherwise MorpheuZ will be confused and won't work anymore.
3) ...or you can edit truetype font preferences in AWeb's "Browser settings" section and delete all the fonts EXCEPT "Normal" and "Fixed width" fonts. Hope it helps.
I'd recommend to try the point 3) first so you can keep your AWeb in truetype suit (provided the solution will work of course ;)