need help fast!!

[jaks7124]

My gas mileage is dropping fast. I've cleaned my MAF, and I read something about cleaning the IAC, but I have no idea where its at and what to do. Also where is my O2 sensor and what does it look like. I have a 91' with 156,000 miles on it. I'm pretty sure that it is time to replace the sensor. I also read something about retourquing some intake manifold bolts--where are these and what do I do? Sorry to sound so ignorant but I've got to learn somewhere. Also one more question--When I start my X up after it has been turned off for a while it has a loud whining noise that goes away after a few minutes, is there any way to fix this annoying sound. Thanks

 

[BroncoIIGUY]

Hmm im not sure im much help but the O2 sensor should be on the air intake, im not quite sure about anything else, sorry bud

 

[Savage Wolf]

the O2 sensor is on the exaust between the motor and the cat, there is either 1 or 2 sensors depending on year of the truck

 

[Audio_1]

mine did that one...........i replaced the air filter and everything was fixed