the MAF measures how much air is entering the engine. This lets the comptuer know how much fuel to inject. If it gets dirty the readings aren't as accurate, hence bad mileage. You dont want to use anything but actual MAF sensor cleaner. Anything else can leave a residue on the sensor and it still won't read accuratley.
crawl under your truck and look at the exhaust. There will be a muffler towards the back, and there may or may not be a catalitic converter more towards the front. If there is a cat then there will also be an EGR valve in the engine compartment. The other way to check is to look at the codes in the glovebox. If you have the code "FE9" then you won't have a cat or EGR.
Oh, and DO NOT touch the little wires on the MAF sensor. the oil from your fingers can ruin it. Only hold it by the outside.
