As LeoTechnoSoft stated, the un-install error which you received can be ignorred and is a known error in the 04.03.00 uninstall script. You can confirm that the uninstall completed sucessfully by checking that:
1) the site's \bin folder no longre contains two assembly files named DotNetNuke.Modules.Feedback.dll and DotNetNuke.Modules.Feedback.SqlDataProvider.dll
2) The site folder \DesktopModules\Feedback is either empty or does not exist.
3) The database tables Feedback and FeedbackList have been removed.
4) The database stored proceedures related to the module (all containing Feedback in their name) have been removed.
Having spent much time installing and uninstalling Feedback 04.03.00 while working on the newest version (05.00.01), I have not noticed any sitewide performance issues related to the module and would suggest that you investigate other causes of the slow performance. That is especially true for the sitewide inability to view the text editor, loss of colour and loss of images which should not be affected by the installation of Feedback module. Have you recently upgraded the site's DNN framework version or installed a new skin?
For example, have you checked your site's Event Viewer not only for recurring errors but also for the number of events contained in the log. Having a large number of events stored in the EventLog database table is one of the primary causes for a slow site. When logged in as host, the Event Viewer provides a link button to click to delete all the entries from the log. Don't do so, though, until you have checked for recurring errors.
Other log tables (SiteLog and ScheduleHistory in particular) can also grow in size to cause slow performance.
Finally, it is possible that the MS SQL Server transaction log has grown too large and needs to be truncated by performing a database backup/log truncation (outside of DotNetNuke).
After you have solved your performance problems and if you would like to try out the new Feedback 05.00.01 module, a release candidate is available on CodePlex:
http://dnnfeedback.codeplex.com/relea...