I've noticed when the barometric pressure is high, my truck tends to get very good gas mileage and super power. When the pressure is dropping, it goes down a little bit... any ideas?

I do know that it is used in conjunction with the MAP sensor.

Also, where on the 4.2l is the BARO sensor located?

 

On my 97 it was part of the MAF functionality. I'm guessing it's part of the MAF in yours as well.

 

Not a big secret. Higher Baro pressure means the cylinders are able to draw more air, the PCM meters more fuel to keep the A/F ratio the same and you get more power. Colder temps do the same thing.

 

Thanks for the input.