hissing sound on and off near the muffler

[JDM-51R]

hey guys,

ive been googling for nearly 3 hrs in trying to find what the hissing sound near the muffler. it just started to happen this arvo. its weird cause its on and off.. ive been reading past threads and what they have been saying that it could be the fuel pump and it being hot can cause it to make a hissing sound.

im hoping someone has experienced this issue before.. please help

i dont know if i just need a new muffler or what...

[Limbo]

if there is leaking you will see black carbon coming out of the exhaust system pipes

[JDM-51R]

none.. its just all sound....