Hi Connie this is lostrider,
~Does the noise sound like a car wash vacuum cleaner?
~Can I get your 17 digit vin number to determine which 4.0 engine your truck has?
Thank you for the reply, there is a valve located on the upper intake called the Idle Air Control Valve, it controls the amount of air entering the engine to maintain proper idle, that valve will get carbon fouled and cause the noise your describing, I know you said the noise is around the air filter area but the valve will cause the noise to move through the air intake hose into the filter housing, when the noise is happening, you can take a small hammer and tap on the valve to change the pitch of the noise, here is a diagram of the valve so you can locate it on the engine, hope this helps.
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