some where that there's no paint. you need bare metal for a solid ground.
or take them off and sand where they are now, till bare metal. bolt them back up.
also make sure your ground straps are in place by the battery to body. they keep the whole car grounded, its just a wire, nothing like a battery cable.
and of course double check all of the wiring from the install. and then last but not least take them off and put back the stock lights, and see if the problem goes away. for all you know its still there and your chasing a bad FM signal.
XM rules btw. ive had it for like 7 years now, cant live with out it now.
