vacuum

Has anyone else had this sound before? It sounds like an HVAC issue or Vacuum leak that when under load at low RPMs and accelerating it makes the suction sound then its almost like a valve or door quickly seals it shut. Ive had this 2.3L base 2 door since October 2022 and it started happening...

On the 2021 Bronco tech specs sheet, I noticed the following: The 2.3L gets vacuum brake boost, while the 2.7L gets electronic brake boost. What is the difference between the two systems? I haven’t been able to find much information online. I’ve also noticed a few other differences between...