How to boost FM Radio Signal Reception on Prius 2011

You might try removing the antenna, lefty-loosey, and see what the fastener threads look like. There is an integral rubber seal between the antenna mast and the base that is notched to prevent it from wiggling loose. If the threads are not clean, bright chrome, then this is probably where your problem is. Corrosion can cause resistance and capacitance issues which can block RF signals. Clean things up, including down inside the antenna base (difficult to get to, I know) and apply some suitable lubricant to enhance waterproofing around the rubber seal. I would personally use some dielectric grease, like you would use on a spark plug boot, but I'll leave that up to you. If everything in there is clean, then your problem is at the other end, up inside the dashboard where the antenna cable plugs into the entertainment system control head. Could be a damaged receiver too, something like a lightning strike. Try the easy things first.

 

Any aftermarket mods to lights, etc.?

I put some nifty LED replacement headlight bulbs in mine. Love the light, but the FM reception is awful whenever they are on.