Tourneo Custom 2018 Pipes while giving gas

Hello together, I have a Tourneo Custom BJ 2018 2.0 Diesel that gives noises when giving gas whistles. V-belts have already been changed and the spinning roll should be OK. The workshop said the whistle noise would come from exhaust gases whistling past the cracker seal. Has anyone had this problem already and can give more information about it? Greetings David