Popping back through muffler on deceleration

Hi guys , 07 xx with yoshi muff on her , k&n air filter . Looks like it’s got a tuner of some type under seat . Not sure when plugs changed they are a nice colour on electrode . Bike starts and runs nice but then sounds like it gets Rich and stumbles at idle , it rides fine but when throttled back starts popping back through muffler . Thinking of puttin new plugs and genuine filter in . What do you guys think ? . Any help appreciated 😊😊. Nick