Ok you guys my 01 3.4l has picked up a whistle under acceleration pretty much all the time now. I can’t find it. It’s coming from back side or under intake in fuel rail area. Sounds like vacuum screech really to me. I’ve changed a bunch of vacuum related hoses and connectors and the egr, map sensor too. I have pulled the coil pack off and started engine to see if I could find it. Used stethoscope all over the area I believe it to be to no avail. This all began the first time I turned on the a/c a couple of weeks ago after using the heater all winter. It seems to be running fine except it doesn’t seem to be shifting properly but that could be in my head. I am getting valve noise at 4000 rpms too though so no real top end. I am trying to clean injectors and system now. I’m going to try to make a video of the noise today while I’m fiddling with her. Any ideas????

 

Could be an exhaust leak. I had a manifold gasket blow a hole in the past that made a loud whistle sound under acceleration.

I replied pretty much the same info on the other post you made. -But its better to make a new post like you did here.

Edit: I guess it could also be an intake leak also. Idk, just a couple things to check.

 

I actually believe an exhaust leak would change the pitch of the engine. It is running great in the parking lot. Lol. It does go away but it does come back too after I stop and shut the vehicle off. But like I said it goes away. It’s like a screeching whistle that sounds like a vacuum leak really to me but where?