just create a filter. put this in your Controller.cfc init():
<cffunction name="init">
<cfset filters("NoDebugForAjax")>
</cffunction>
<cffunction name="NoDebugForAjax">
<cfif IsAjax()>
<cfsetting showdebugoutput="false">
</cfif>
</cffunction>
remember that you will need to edit your other controllers that you
have an init method in and add:
super.init()
as the first line of the init() method. otherwise the init() method in
the Controller.cfc won't run.
might be a good idea if wheels did this automatically. i don't see any
reason not to and it can be handled by the dispatcher.