Newbie question on rear of car swishing noises
 

So lately when I do a full stop or near full, I can hear swishing noises from the rear of the car(I took out all sprays/etc from trunk to ensure), Im guessing its the gas tank? I just want to be sure its nothing serious.

Your car is fabulous?

Really though, are you sure you're just not getting more attuned to your car's normal noises that perhaps now you're just noticing it?

On a rare chance that something has come loose, you could see if your dealer has another FR-S you could test drive to see if you can duplicate and determine if it's worth having service take a look at your car?

Can't imagine it's debris or even ice, but I've been surprised before...

Fill the gas tank and see if it goes away.

Tanks about 3/4 full when I noticed the noise. Definitely didnt notice it when tank was full. Ill try to check under the car to see if anything is stuck under.