Toyota Repair: air valve, coolant hoses, gas milage

Question
I have a 1990 4 runner V6, my problem is bad gas milage and performance ( can not get above 80 mph). I went thru the haynes repair manual cks for the fuel injection system.When I checked the air valve, It tells me to adjust the idle screw all the way in while the engine is cold and the rpm should drop , after it has warmed up there should be no drop in rpm. According to this check my air valve is bad. My question is where is the air valve? the manaul I have shows a pic but Ihave not been able to locate any valve with coolant hoses going into it. Thanks Ron

Answer
The rpm will change when the adjustment screw is turned when the engine is warmed up at idle, it has no effect when the engine is cold and at fast idle and has nothing to do with driveability or loss of power, I don't know what air valve the haynes manual is referring to.
The problem is elsewhere, check for a possible engine misfire, check the basic engine timing, these engines had headgasket problems, so you may want to check for that possibility.