Shissing and whistling sound and checks gages on

check hoses for leaks or if they are disconnected

Depending on the whistle, fist check the vacuum lines.
There are many under the hood.
One way some people test them is to listen most carefully whilst the motor is running, and then take a spray bottle of water and spray it where the whistle sounds like it is coming from,.
If the sound stops, the water has found the hole and has plugged it for a second, and helped you find the leak.
Other whistles can come from a pulley or part that is failing, and that part is telling you ahead of time of the problem.
Be blessed.

check the PCB balve maybe is cloged and the breather that create high vacuum wen are cloged and create a whistling sound.

HELLO, Check and see if the catalytic converter is stopped up. You can do that by removing the oxygen sensor in front of the converter (be careful you don't catch car on fire) or you can have a back pressure gage installed in the exhaust system that will tell you if the exhaust system is stopped up.

check vacuum lines it sounds like a vacuum leak a vacuum line will whistle when it is sucking air.

Plural husbands? Check each wheel by jacking up that corner of the car and spin each wheel by hand. If one of more of the wheels makes this sound, there may be an incorrectly installed pad in the brake assembly which could be dragging on the rotor. Make sure that each caliper will retract properly. Hope this helps!

Turbo vehicles often sound like they are whistling when the turbo spools up because it is sucking in air at a high rate and it makes a bit of a whistling sound. Generally not a problem unless it is a different whistling that you are referring to.

it sound more like you have a vacuum leak then a bad fuel pump that's why you keep getting lean codes have some one rev the engine slightly while you listen under the hood for the whistling noise the whistle is the vacuum leak

Often a whistling sound, from the engine bay anyway, is the sign of a vacuum line that is leaking. Might want to check all the vacuum lines for cracks and such and make sure they are all connected.