Ok, this is a super annoying issue but not life threating but I still want to figure this out cuz I'm gonna hand this beast over to my younger bro soon and it will drive him nuts. Shes a 91 2WD V6 with 200K on the clock. When you apply the brake pedal from about 50% to 90% of the way, whether stopped or moving theres a whissling noise thats pretty loud and it changes volume according to the pressure applied to the pedal. It happens a lot more when the vehicles is warmed up or its just warm outside. and as soon as you let off it goes away. The noise is coming from the engine bay down around where the brake pedal sits and I imagine that its air escaping from something or whatever but I don't hold enough tech experience to know exactly. Any ideas on what needs to be replaced or repaired would be great.
Thanks, rook