Import Rule Extension Issue

Making changes on a custom import rule extension - issue is, changes don't seem to get picked up when MA runs sync.

Export sections picks up edits, but import does not. Very strange.

Code I have implemented just to check:

void IMASynchronization.MapAttributesForImport(string FlowRuleName, CSEntry csentry, MVEntry mventry)
        {
            switch (FlowRuleName)
            {
                case "cd.user:msExchMailboxGuid->mv.person:msExchMailboxGuidString":

                    throw new UnexpectedDataException("UPDATED");


            }
        }